Caulking. I have caullked in three of the last five places I've lived because the kitchen sinks and bathtubs get left for so long not only is there black mold, but the caulk has dried up and is pulling away. Which creates access for water to seep into the wall, thereby creating mold INSIDE the wall. Now there's a pricey fix... My caulk jobs also look better than the one the landlords did in the fourth apartment.

Seriously, if I had my druthers, I would put that shit everywhere. xD

Other than that, learn to monkey around with stuff. I draw the line at electrical wires and garbage disposals, but I've learned how to do simple fixes in a toilet and a stove just by playing with stuff 'til it works again. I also think it's pretty fun!