FIFA 11

Certain players in FIFA 11 has traits/ specialties attached. These include "playmaker", "crosser", "aerial threat", "distance shooter" and "poacher". If you perform certain tasks with a player with these abilities, you'll get an achievement.

One of the ways to get the "Crosser" achievement is to play as Manchester United and put Ryan Giggs in the starting line-up. Keep crossing the ball with him and if someone scores a goal from his cross, you'll unlock this achievement.

You can do so on any difficulty level. I won this achievement on Amatuer.

PS: Since Nemanja Vidic (aerial threat) and Dimitar Berbatov (poacher) are in the same Manchester United team, you could do all three achievements in one game.

This can also be done in the practice arena, go to team management, player roles and make sure the corner taker for the team your pro plays for has the crossing abililty.
(I did this by accident while my pro was signed for Chelsea so their default corner taker must have the crossing ability).

Now just practice corners until you score.

Further to the excellent solution written on the guide for the 'Aerial Threat' achievement by HollowxIchigo15..

I would just like to add, it may be worth doing what I did and playing 2 Strikers both with the 'aerial threat' ability to speed up proceedings.

So just to emphasize:

Kick-Off > Exhibition Match
Team: Rest of World > Classic XI
Opponent: Any 1-3* team just to make things that bit easier, or even randomise the selection if you're not fussed!

It may be worth putting on 20 minutes half lengths so that you don't stress over time remaining in the shorter matches.

I changed the formation to 4-4-2 and played;
Zico (right footed crosser) in the 'RM' position,
Hugo Sanchez (left footed crosser) in the 'LM' position
Alan Shearer and Rudi Voller in the RS and LS positions who both have the 'aerial threat' special ability.

It's makes it a whole lot easier with this team crammed full of mid-high 80 and low 90-ranked players,

For an average FIFA player such as myself I managed to get a cross from Zico headed into the back of the net by Alan Shearer on the '8 minute' mark of a match against West Bromwich Albion.
Netting me 20G for 'Crosser' and 'Aerial Threat'.

Select a player with the Crossing Speciality, Giggs(Manchester United) is one of them. Keep crossing the ball with him and you will have it in no time. Remember to play on amateur.