Most of the signing I do with Nate is in the context of our everyday conversations. I tend to sign one to three words per sentence. Here is a typical conversation during lunch (the capitalized words are signed as well as spoken): "Do you want to EAT MORE food or do you just want to keep throwing your AVOCADO on the floor? Oh, your HAT? You want your HAT? Here's your HAT. Oh, THANK YOU for smooshing your AVOCADO on your HAT."
Another easy way to incorporate signing (especially for things you don't talk about in everyday conversation) is to sign while you read to your baby or toddler. It's more important that you use a few signs regularly and consistently rather than many signs sporadically. To start, learn a few relevant signs for your child's favorite book. The dictionary at www.lifeprint.com is a great resource.
You can sit your child facing you, so that he can see your face & hands easily while you sign. Or you sit your child on your lap and make the signs on him or the book. For example, if you were to sign BIRD you could move your finger beak in front of your own mouth, in front of your baby's mouth or just on the book itself. Do whatever is most comfortable for you. Just don't forget to speak the word as you sign it, since the ultimate goal (or one of them) is to teach the meaning of the spoken words to your hearing child.