Muliclass is a early game strength
Bard fighter and paladin make the best first level options giving skills equipment and attacks at the beginning
Sorcerer, cleric, wizard and fighter all make strong 2ns classes for the spells or attacks
Bard, druid and warlock tend to be better off staying pure because what you gain from multiclass generally can be covered elsewhere without lossing feats or spells
The rule of 4 = feat
The rule of evens = extra ability , be it spell or attack
