I started to rehydrate, but not make starters. There is SOO much more yeast in a dry packet than in a liquid yeast pack that it's cheaper and easier to just pitch it. They are also pretty cheap, so I use 1 packet for up to like 1.060 wort, and 2 for anything over that.
To rehydrate, I sanitize a small glass, or a very small mason jar by spritzing with starsan. And spritz the yeast packs, and piece of aluminum foil big enough to cover the glass, a fork, and some scissors. Grab a room temperature bottle of spring water and after the 30 seconds is up, pour some water into the small glass. Then cut packet and sprinkle the yeast on top of the water and cover with the foil.
Let it sit for 15 minutes, gently shaking to distribute the yeast a little bit. After the 15 minutes, stir the yeast into the water with the fork, and pitch it.
Rehydrating will fill the yeast cells with the liquid they need to get started, without introducing components into the cells that can hurt them.
You can also pitch right on top of the wort and it will be ok, but according to the yeast makers' instructions, rehydrating is the better option.