I wish you luck on your endeavor! A Let's Play can be something very enjoyable to create, and to watch if done properly. I've not much experience with creating them myself, but I've done a lot of looking into them.
I do have a few recommendations though. Preparation is key for a successful Let's Play. Recording a play through of something that you're not 100% familiar with, may seems like a decent idea at first, but more often than not your audience will suffer for it. It's imperative that you play through the game or levels beforehand, and know exactly what's expected of you within the game. Trust me....there's no fun in watching someone backtrack through half a level because they forgot to pick up a key for the next puzzle.
Another thing is to make sure your audio recording and video editing skills are competent. If we can't hear you, that's a problem. If their are anomalous and annoying sounds in the background of the commentary track, that's a problem. If you're videos are filled with needless pre-game junk, substantial event-less backtracks, or unnecessary scenes; it's a problem. If you're recording via camcorder, I would rethink you're first attempt at a Let's Play.
I would also recommend that you decide on a theme for your lets play. By that I mean there are many different types of lets plays: A straight play through of the game (much like a visual walk through) with minimal commentary, A play through with a commentary that acts like an interesting factoid about the gameplay elements and creation of the game. Fast and loose play through featuring humorous commentary (with one or several commentators), and so on...
The more structured and well put-together your Lets Play is, the more likely you will maintain an audience past the first video. As a reference, I suggest that you check out the Something Awful Let's play archives. Some notable LP'ers to examine would be those such as: Slowbeef, Chipcheezum, ResearchIndicates, Proteus, many more. Their stuff isn't amazing, but it's a good example to go by.
Again, good luck!