Also, a sufficiently high Fast Healing, say fast healing 10, has a higher LA cost than Regeneration 10.
Non-abilities are calculated as if they where +0, so if a creature lacks con for example, it is considered to have a con modifier of +0.
Alternate modes of movement (such as flight and burrow speeds) give a LA adjustment of +1, but strangely swim speeds do not give an increase to LA.
Some creaturetypes (such as plants and elementals for example) increase LA by +1. This has to do with the immunities the creature type gives.