It'll be something that comes with practice. Make sure you're going into the same part of the chain every time, and that the chain doesn't twist. It can be tough sometimes. I've been crocheting for 10 years and I *still* have issues sometimes. If it isn't coming out how you like though, you can always pull it out and start over.
Another suggestion, do your chain with a larger hook, 1-2 sizes bigger. It'll help your edge be a bit looser and easier to see the chain stitches.