Each character has a different style of fighting.  Each of the
characters skills must be harnessed during battle.  Here are the easiest
ways to fight with each character.

Shrek: Just punch, if he gets hit he can take it

Fiona: She is strong and average speed but is still easily defeated. 
Your best bet is to find an hourglass and activate slow time.  If you
can't activate slow time run.

Donkey: Jump attack and then use his special.  Repeat if necessary.

Gingerbread Man: Jump attack is your only hope other tahn running or
your special.  Let the others fight for you.

Lil' Red: It's hard to fight as her so just throw apples and hit targets
that get to close.  If you need space, jump attack.

Puss In Boots: Jump attack then slice your opponents up with his sword.

Big Bad Wolf: Just fight or use your special.

Fariy: Hold the attack button after finding a target.

Shrek&Donkey: This is a different character.  Use your special then
attack like mad.  After a while run.

Note: This tips do not relate to hero time, each hero time (except maybe
Big Bad's) concentrates on that hero's strengths. This dose not make
them any easier though.