There are some great tips in this 7 minute video by makeupmestunning. I thought the most helpful tip was that if you avoid using mascara on your lower lashes because you think it's too messy (I do!) try using black eyeliner on your lower lashes instead. What a great idea!
You may also be interested in checking out Save Makeup Save Money: Tips for Making Your Beauty Products Last by HSN beauty expert Lara Ramos.