1. Test first.
Test out some different styles of topstitching to see which one looks the best. A single stitch creates a thin line while triple stitching creates a much thicker line. Contrasting thread pops in your projects while matching thread is more subtle.
For this thick fabric, I opted to do a triple stitch because the single stitch was just so invisible on the fabric.
2. Press first
I hate pressing but it's always a good idea to press the seam you are going to topstitch so you get a nice clean fold on your fabric.
It can be very tempting to speed along but going slow is key to getting a smooth, straight line.
4. Find somewhere to line up your fabric.
Having a guide for your fabric is a must! I like to use a machine foot that lines up with where I want my topstitching to be. You may need to try a few before you get one that fits. Also, you can use a post it note on your machine if you need to line something up in an unusual place or deep into the fabric.
Be careful! Not all positions on your foot are equal. On one side I lined up the seam with the center of the foot and had the needle in the left position. On the other side I used the center needle position and had the seam run along the inside of the left prong of the foot. They didn't come the same width. This goes back to #1 Test first!
5. DON'T PANIC!
Don't be overly stressed if it's not perfect! You can rip it out and do it over if it's really bad but most people won't be looking close enough to notice all of those little jiggles in your topstitching lines.