Clicker training involves several physical (mechanical) skills - watching your dog for the behavior to happen, marking the behavior with a click (i.e., knowing when to click - TIMING), and delivering a reinforcer to your dog. Lucky for us, these skills overlap and they get better with practice! For example, improving your observation skills will naturally improve your timing on when you click for behaviors. :)
When I first started clicker training, I was clumsy and my timing was off. It felt awkward and slightly embarrassing :). But practice does bring improvement and as I became comfortable, I got loads better!
Silly dog, practice is for humans
Before you start clicking away with your dog, it's a good idea to practice your skills sans dog. This will allow you to get comfortable with the mechanics and gain some coordination first :). There are plenty of clicker 'games' out there that you can play to improve your timing (and also your observation skills).
Here is a great video with two common clicker games:
Another fun game you can play requires a human friend :). Get together and decide in advance what behavior you are going to click - for example, raising two fingers like a peace sign. If your partner raises one finger or three fingers, or any other combination of figures, you don't click, but the instant she raises two fingers in a peace sign, you click.
You'll start to notice when you have played these games and practiced your timing, you have also improved your observational skills. Win-win :). Now that you have practiced your clicker mechanics to a level of comfortableness, it's time to add the dog!