If I can share with you one tip above all others, invest in a good paper trimmer! I am talking about a full 12 x 12 minimum size. Not something that only trims papers, or a paper cutter, but a normal paper trimmer like Fiskers SureCut Paper Trimmer (Z1783). While it seems like a hefty price at 34.95, you can take a craft store coupon and get one for less. You will find this tool indispensable. Did you know you can also use it to score your cardstock?
There are two ways to accomplish this, purchase the scoring blade (Z1785) or remove the blade and place your cardstock in as you would if you were cutting, then using your bone folder or a dry embossing tip, gently run down the cut line. This is a great tip when you want to score the entire 12 x 12 piece of cardstock.