I think a good mentor is essential. But depends what you mean by mentor. I am a prop trader and working with successful traders and talking to them and having a level of trust where you can talk frankly to each other about your trading has been a huge factor in my profitability. However some "guru" who talks to you via Skype and claims to be a big trader is probably just as likely to be looking to you for ideas. Any mentor worth his salt will let you sit with him as he is trading in the live market, with real size making real money. i remember when i first started (about 6 years ago) watching someone nonchalantly pull 5k out the market scalping Bunds in about 45 minutes, that leaves an impression on a young kid starting out. But some guy showing you a head an shoulders pattern on EUR/USD and claim to be short from the break blah blah give it a miss
It is difficult to come up with the right questions. There are four or five that must be answered. For me only experience could teach me the correct questions.
There is another very helpful forum where traders explain their methods. Sort of a virtual mentor. I highly recommend it. PM if interested. But in the end you'll have to find a method that "speaks to you" and fits your personality. You'll want to stick to this method and not bounce from method to method. I absolutely do not recommend paying more than $50-$100 in TOTAL EDUCATION COSTS. Including books. There are plenty of free sources on the internet and any money spent beyond this amount should be used to practice (funding for a data feed).
I think you have to luck into it nowadays. Maybe in the past you could hang around the stock exchange and with enough persistence eventually find someone. But now that everything has gone electronic and much of the industry has withered away, the good traders are harder to find than ever. I did some online searching earlier this year but couldn't find anything that satisfied me. I think you just have to luck into meeting someone who likes you enough to be willing to work with you.
You need a mentor you can trust. Anyone who says you don't might be a little self-absorbed. Otherwise you're going to learn and recreate a lot of bad mistakes over and over and over. Best to get them out of the way in the beginning instead of trying to erase them later on.