I don't think it's all that important to have one particular mentor that's sort of a formalized relationship. I do think it's important to surround yourself with people - preferably in a face-to-face environment, like a job or coworking situation - that have done this before and have a bunch of experience in development. Observe them carefully - not just the product of their programming, but the process they go through to create it.

I disagree with the poster who says Google is your mentor. Google's great for sticky questions that nobody knows the answer to. But Google will never tell you that you should be asking a question but don't yet know that it's a question worth asking. A lot of things in programming are like that: you'll see someone do it and think "Why didn't I think of doing that?", but the reason you never thought of it is because everyone who does it considers it too obvious to be worth blogging about.

You don't really need a mentor to start. You just need to dive in and start building something you like. Also, stop being a perfectionist and following tutorials front to back. Google is your mentor.

If you really get stuck, there are mailing lists, IRC chat rooms, message boards out there specific to that topic. Explore them fully, don't be afraid to ask a question. But before you ask, make sure you've made some effort to find an answer.

Having one or more good mentors will certainly speed your way towards becoming a "strong developer". And all the points nostrademons makes are true.