nice question, for me i will checking first account must be real and both track record and trading privileges verified.
the second thing i will see what broker he/she use. of course the reputable brokers is good choice, in this case i prefer to see if brokers comes with strict regulations like cftc, fca, asic.
next check is drawdown, dd is another important factor. for me, drawdown 5% is good choice if account above 10k, and for a few thousand dollars i think 10 - 20% is normal. for starting deposit few hundrets dollar 50% drawdown is still normal. of course you must compare drawdown and return, the good sign is return must 2x drawdown or more. for example : if you see drawdown 10%, gain must be 20% minimum.
and the last the most important thing is checking average win,average loss and profit factor. good system must have average win higher than average loss and profit factor minimum must be 5.0 why? because this indication of risk reward, did you want your 100 winning trading trades vanish because 1 losing trades? sure, nobody ones want it. Every one want 100 losing trades can be recovery only 1 winning trades. yup that's it. I hope this can help you choose the good system.