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.