Fees for Lease Violations?

[Angie B.]

After our last tenant moved out, I reflected on how she left the property (it was not good) and how through the 2 years she lived there, she violated the lease several times (unauthorized occupant, changed locks, etc) and every time, my husband would say not to make a big deal of it, she pays on time, everything else is fine, it's not a big deal, etc etc. Fast forward to the end and she had an additional pet and had smoked in the place the last several months. I think by that time we appeared "laid back" about the lease, and I don't want that to happen again. So I need to be able to enforce the lease without necessarily evicting someone- and I'm thinking charging a fee sends the right message. I found the thread below, but would like to see what others charge as far as fees for lease violations.

http://www.biggerpockets.com/forums/52/topics/120987-dis-incentives-fines-for-bad-behavior