Yes, definitely measure and pin your border. I used to do the same as you, but my borders come out much better now that I take the time to measure, cut and pin everything.

I do mine like Bonnie Hunter from http://www.quiltville.com

I lay out my quilt, layout the border fabric in the center of it, smooth it down and cut off the extra. If it is longer than my table, I pin it every so often so it doesn't shift, then I fold it up a bit at one end until the rest fits on the table, then finish smoothing and cut off the extra. What she says is that measuring tapes don't drape the same way that the fabric does. I've been doing mine this way for a while and I never have wavy borders. She's got a "printer friendly" version of the instructions on her website. Here is the link:

http://quiltville.com/borderhintspf.html

One of the guests on one of my quilting shows said she always sews the quarter inch seam on her border piece before attaching it to the rest of the quilt. (you will sew over it again, when attaching.)
It's like stay stitching and she says it keeps her from ever having wonky borders.
I haven't tried it yet, but I've sewn clothing all my life and stay stitching is an awesome technique.
I hope it works out for you :thumbup:

Also helps to fold the quilt in half and mark with pin then do the same with the binding. Match the pins together and insert pin to hold. Divide the halves on either side of the center in half and do the same thing. Pin every so often in between then sew. If there was ever a time to use pins it's now, in my humble opinion.

Try using a walking foot so both top and bottom pull evenly.

I use pins and quarter in the middle and then between the middle and the edge. I also measure in the middle to get the right length and width. It works every time.
Deb hope this helps