As trumps are the hightest cards, try to keep high ones till the end. Attacking with trumps in the beginning will only gift your opponent a good card. So better try using them to defend when not having the needed card.

If playing with "Attack transfer":

Keep in mind that if you attack with cards of the same value for example two sevens, you should not put them together. Why?

If your opponent has a third seven he can attack you with all three! 

Although you could have transferred the attack later if you only put one seven and then the second one after.