It does depend on what you value the most: learning and risk or security and safety.

Having been through 4 startups and 2 corporates - nothing beats the range of things you will do and learn in a startup and the speed at which everything will happen. You'll make some amazing friends and see something grow (hopefully!)

If you can't handle change and uncertainty then stick to corporate, else startups all the way....

Some great answers here which mostly say the same thing: revisit the customer development / validation part as it appears you may not have done this correctly or in the best possible way.

You know from the results you've got that growth and repeat usage is not occurring (let alone revenue) and while it's tempting to think "perhaps we haven't found the right marketing channel yet" or "if only we gave it a bit more time".. the most obvious answer is always "this is not something people really want".

What you really needed to hear in customer development was "one of the biggest issues I have in restaurants is that I always get confused about what to order and it's a big problem for me. I'd happily pay to use a service on my phone which would tell me what to eat based on my preferences"

What I think you might have got is:
"sounds like a neat idea - i'd give it a go".

which really translates into:
"it sounds a bit of fun and novel and I'd probably try it out once and then never bother again. It's not really a problem or issue I lose sleep over to be honest"...

A co-founder is really a necessity these days as there is so much work to do and speed of execution is so important.. that one person on their own is at a real disadvantage.

Combine this with starting a business being really hard with many huge ups and downs.. a co-founder helps bring you up then you're down.

I've built 2 businesses with a co-founder and 2 without and would choose the former EVERY time.

In terms of where to find them, I'd consider a few sources:

1: Contact people you've worked with in some capacity before and got on well with, even if they're in a job (you never know what they're planning to do next)

2: Use Linkedin to find people in companies or with skills you have identified you need and just reach out.

3: Consider joining programs such as Entrepreneur First (www.joinef.com) if you're in the UK - which specialise in taking technical talent and matching them with co-founders before the idea and business is formed.

4: By all means go to startup events and hackathons and network around - although I've never found this an optimal use of time.

Once you've found someone that might fit the bill - suggest you work together on a specific task or project for a few weeks and see how you get on. If you're being productive and enjoying the time together - keep doing it. Else don't be afraid to break it up and try again.. better to have no cofounder than the wrong one.

I've been in two startups with international teams - technical ones in different countries.

I agree with the other answers here that technology now is superb at helping people keep in touch - e.g www.slack.com - so collaboration is much easier. You need to make sure they're always part of the team and feel involved. I know one company who puts a tv screen in their office and has a live Skype video feed playing at all times so everyone can see each other.

Just be careful about giving them the VP or CTO role though as ultimately that person will be building the tech team and they'll only be able to do that back in the US... so if you're happy with all team being there then that's fine.. else Senior Developer is flexible enough.

What ever you decide - get them either on a contract basis or bring them into the team with equity - but make sure it has a good vesting clause (i.e. they earn shares every 3 months until the agreement is terminated).

I've been on both sides of the table - as an entrepreneur that has received external funds twice, and as an angel investor putting money into 8 early stage startups.

Best to break into 2 sections: a) the business itself and b) the actual investment deal on offer

**The Business**
You'll always find risks when running through it - but that's the nature of these things. They're trying to build and de-risk in stages which is why they often need the cash. Earlier you invest, the less that has been proven. So just bear that in mind. Things you want to look for:

1: Why does the business exist - is it a good enough reason and solving a real customer problem? (ideally a painkiller not a vitamin; nice to have)

2: What does the market look like (size and growth) and what opportunity have they identified within it? Is it a bit enough sector that they're addressing.

3: What's the product / solution they believe takes best advantage of the opportunity outlined in (2)

4: Why that team and now? What's so good about the team doing it and why are they the best people - do they have something special which gives them more of a chance than another team? Can they execute quickly and beat off the competition? Make sure they've got the right mix (tech, product, sales /biz) and that they're all fully committed and not half -arsed (doing jobs on side)

5: What do the business economics look like. Have a glance at forecasts but they will only really know the next 12 months and are guessing the rest. Look at the levers / drivers of growth instead and see if they are realistic... e.g. if revenue will grow 30% - what drives that revenue - higher order value for example.. if so how will that be increased and does it sound reasonable..

**The Deal**
1: I usually expect that I'll get diluted by 1/3 and then 1/3 again at some point.. so I'm always asking "what if they grow to £X revenue over 5 years" - how much % would I have then and is that a decent return. Often you can say "I think they're 30% likely to get there and divide your numbers by 3 to factor in the risk"

2: Are you getting the same share rights as the other investors -make sure you are. Nothing is worse than a VC coming in and getting "preferences" over your stock (i.e. they would get their money back first in any sale event and only after that would it all be distributed equally)..

3: Are the other investors well thought off and highly sought after... if they've done their due diligence and believe in it - that's a very strong signal. Make sure a good % are following on if there has been a previous round too

4: Be careful with the valuation as a lot get hyped these days. The higher the valuation - the more risk the company should have reduced. If you see a high risk, very early company with a large valuation - be very wary.

Hope this helps - very happy to go into more detail over a call if you like.

Investors like to build relationships over-time... you hook them in with something interesting you're doing and then gradually keep sharing your progress and achievements even before "officially" fundraising.

AngelList is a great source (for Europe and the US) in getting to know which are the key investors with expertise in your sector and actually make investments (which is key). Find the companies they are investing in and contact the founders of those businesses asking if they have a good experience with them and might be interested in making an introduction for you.

A lot of early-stage and angel investors get good deal-flow and often now limit their correspondence fro warm introductions from people they know - so you need to start with that. Following and interacting with the investors via Twitter, Quora, and their blogs - with insightful points - will also earn you a few brownie points.

For Europe, this is the best crowd-sourced list of investors there is: https://docs.google.com/spreadsheets/d/10S7_jBpRoWuNMnOYpkjFJArt76dPhFw0tIR7E_ndgnk/edit#gid=0

If it was me right now... I'd research 5 of the best angel investors I could that seem to be active and focussed on the type of business I was in, then reach out them via email and/or twitter. A very brief email noting why I was contacting them (they've invested in similar businesses) and a few quick lines what my venture is - with a one page summary PDF attached (nothing else). I'd also assess my network to see if anyone knew them directly and could put in a good word for me.

Hope this helps a little bit in getting started,

This question really does depend on if you're talking about B2B (selling the technology to other travel companies) or B2C (you have a compelling travel site or app that a customer can directly use).

On the B2B side, nothing beats patience and focussing on making an amazing product that people understand why they should use it (the value proposition), keep using it (retention), and then recommend and tell others about you. In the travel space, word travels fast and you'll build up a reputation for having something valuable.

To accelerate that you'll want to establish yourself as a company that can add value in the space through speaking at industry events and conferences, hosting your own events where you educate and inform on a particular topic and capture contact details / briefly chat to the attendees, and publishing regular, quality content that again is interesting and engaging.

I'd invested in numerous SaaS based companies of this nature and this approach is by far the most successful, albeit often a slower burn than direct marketing.

You should also look at using Hubspot (www.hubspot.com), and reading the blogs of Tom Tunguz (http://tomtunguz.com/) and Christoph Janz (http://christophjanz.blogspot.co.uk/) that focus on this in particular.

For B2C, it's a very competitive space and happy to go into that too - depending on what your focus is..