First you need a very good free kick taker , it just won't happen if a guy sucks at free kicks , the most important is to have big swerve and free kick accuracy , this will help you get accurate and constantly good shots with good swerve.
And also he should not have alot of shot power because you will not get it past the wall and into the goal because he just has too much power in his kicks and the shot will not fall as quickly , the best power is probably around 75-85 for free kicks as I have experienced.
Secondly you need to practice with your players , they all have different free kick types as you see in edit player where you choose motions of players , and each has different positions where the shoot will go after you fire , so you need to see which player you are using and test your shot too see what position you aproximetly need to take with your player in order to get the ball into the left or right side of the goal and then always take that position.
The final thing to do is the shot itself , the power should be always just bellow half that will produce the best and accurate shot , now the way you take it is simple.
1. Press (shot button) or ( shot button ) + ( arrow down , arrow up )
Arrow up means more power , no arrow just shoot button means middle power , arrow down means less power.
2. after you let go of the shot button press the left or right arrow , wherever you want the ball to swerve in , you can also press ( pass button ) or ( trough ball button ) with arrow keys together , the pass button will provide even less power than usual and troughout button will provide more power.
And for distances aproximetly what I use with my player which has over 90 swerve and acc. and 81 shoot power
16-19m = 1.arrow down , 2.side arrow + ( pass button ) = weakest shot
20-23 = 1.arrow down , 2.side arrow = 2nd weakest shot
24-27 = 1. nothing just shot , 2.side arrow = average shot
etc...