Along with a rotary cutter you are going to want to invest in a "self-healing" rotary mat and a ruler made to be used with Rotary Cutters.
@ Self-Healing Mats - were created to be used with rotary cutters. The problem was rotary cutters cut fabric fabulously, but it also cut what other surface was underneath the fabric. Say you didn't want to mar your counter top, or wood table so you placed a piece of say cardboard under the fabric. The cutter went right through that also and probably pushed the fabric down into the slices it was creating. SO, a cutting surface was created that would allow the fabric to be cut without destroying the cutting surface itself. The surface of the mat is called self healing, because it's made out of a special rubberized surface that can recover from the cutting and be used over and over.
@ Rotary Rulers - When rotary cutters first came on the market, quilters/sewers were using metal type architectural rulers with them. Imagine less than and 1/8" edge to guide the rotary blade down the ruler!!! It's amazing that so many quilters from that era still have their finger intact! Now we have so many awesome rulers to choose from. They are about a 1/4" thick and create a nice straight edge to guide the rotary blade. I love that they are see-through and marked in 1/4" increments. There are many different brands of rotary rulers. Check around, lay them on light and dark surfaces to see how easy/hard it is to see the measurements marked on them. We have the tendency to walk in and buy the first one we see, the one on sale etc. . . But then you begin using it and find out that it's hard to see the marks on dark fabric, or you really wish it marked the 1/8" increments and it doesn't. BASICALLY - test drive a few models to find out which will work best. Start with one ruler and use it a several times before you add to your collection of rulers.
@ Rotary Cutters - Like the Rotary Rulers, there are many different brands and styles. Check out how the blade guard works. How does it fit in your hand? Will you be doing multiple layers of fabrics? or will you cut curves and need a smaller more manueverable blade? Again buy one, and test it out before you buy other sizes etc . . . You will probably end up with more than one if you really get hooked on quilting.