Small talk is invaluable. Being able to fill in quiet moments with questions, thoughtful opinions, or even just a joke can kick off a date well or bring you back from a lull. Jump-starting the conversation could mean the difference between a next date and not hearing back at all.
Here's a handy-dandy guide to help you get the conversation moving.
Another thing to note is how important it is to know your grammar and spelling rules. This is especially relevant in the online dating world; friends of mine have told me that they sometimes won't respond to online messages from potential suitors because they used improper grammar. At the very least, know your "you're" from your "your."
Above all else: If you like someone, tell them. Don't get into the habit of playing games.