Best way I've found so far to get LP is to spam the 1 minute cooking skill with a bunch of sims. Put them all in the same room with a bunch of stoves and toasters, get rid of the door, throw 2 pets into the lot to grab what you can from them and just spam the cooking skill. You get 5 LP from finishing the collection and then you start again... you also get 1 LP for getting your sims skill to 6 if your sims cooking isn't at the top yet. I don't even bother cleaning the dishes and just let them stack up but that is personal preference. And of course the pets can give you LP every now and then too. I got over 50LP in one day and 50,000 coin and went up 2 and a half levels from lvl 21 to 23.