The best way, and very hard to almost impossible, is to find a winning trader who will speak with you for free; perhaps you can work for him or her.
Unfortunate Rule Of Thumb:
Most "mentors" who teach for money do not win in today's markets. They often charge quite a bit up front and then want continued payments.
I was in shock, many years ago, to see the bottom line trading records of the paid mentors at one prop firm: They all were losers who owed the firm money. Another firm I knew very well that was full of mentors for hire; well, the firm went under owing the traders money.
And then there are the legend of vendors who call themselves mentors.
Sometimes market anomalies or regulatory glitches that favor a trader (the old SOES rules) end and traders who had an edge become losers and then they become mentors. Some mentors are wild yahoo's who were lucky for awhile before going bust. Some mentors were never winning traders and are hardboiled liars and hustlers. Some are delusional idiots.
I once walked into a training seminar at a retail broker where the teacher was trading on demo but pretending to be live. Sheesh. But only real rubes would fall for this one.
You are smart to look for mentors. However. Buyer Beware!