1-When making a player a captain does it add anything special to your team ? or it is the same no matter who is the captain ?
I look for a Good performer that makes good decisions = ratings and Creativity, but if it seems not to work for that top guy I promote next top. Is it true? Who knows, it amuses me.
2-Should i consider the foot of player when putting him in a certain position ? it means should i put in DL post a left footed player ? what does it add ? or left or right doesn't matter ?
I look for right or either footed players for DR and MR or L for opposite equivalents. But if a R-footed DL is on the market with good ratings then I'm not going to miss the chance of a 'Tommy Gemmell' But ultimately if they don't perform they're out.
3-Should i buy defenders and attackers with 1 m 90 cm height or + so they score and defend better with their heads ?
I don't really bother - if it makes a difference then an easier game mechanic to implement would be using a 'performance factor' based on balance between height and weight - much simpler to implement in code than actual height factor and therefore more likely imo. But I don't buy fatties or weaklings even if it means I might miss out on Der Bomber. (Apologies to the Mass-ively challenged)
4-Corner and free kicks takers , should i put a left footed player to shoot left freekicks same for corner or the inverse ? or it doesn't matter too ?
Although, if I was a real manager I might encourage a rightie from left and leftie from right for both CK and FK as a starting point, I find same foot/side appears to be better in the game. Commentary does support this preference but having a rule or Commentary bias doesn't matter - outcomes do. If its not working for a player change it, if its still not working change him.