[otter]

A few things:
what hands do they tend to limp with and in what positions? Will they raise A,J in EP or limp? Same goes for late position. Are they more agressive in late? Looser? Sometimes I will note the details of a hand if it was a wild one. Do they bluff? Do they bet small when they have a weak hand and big when they have a strong one, or vice versa? If you notice any betting patters take note of that. Are there any timing tells?