I grabbed an old bra I had that was stretched out, so it still fit. The one I choose had an underwire, though I would suggest going for an old sports bra or at least a bra without an underwire.
1. I put on the bra and made pen marks where my nipples were on the outside of the bra (my mom helped me out a little with this).
2. Then I cut a horizontal slit that would be big enough for the breast shield to fit though (about 1 inch, depending on what pump and size breast shields you are using). You can always start with a smaller slit, and then make it bigger if the shields don't fit though.
3. Put the breast shields through the slits and the pump together, then put your new bra on and Viola! there you have it! You just saved your self $30 and gave yourself a bunch of time to multitask.
If you will only be pumping for your new baby, I suggest you watch this video about how to maximize your milk production. Pumping is great, but it doesn't get your production going as well as actually nursing your baby. This video will show you tips on how to pump and get a good milk supply.