Best way from Gare Lyon, Paris area to CDG

By best, do you mean fastest, cheapest, most convenient, or something else? How many are you? What day, and what time of day? You can take a cab, which is easy with door to door service. People quote fares of about 50-60 euros for this. You can take RER line A from Gare de Lyon to Chatelet-Les Halles, then change to RER line B all the way to the airport. This is less than 10 euros and doesn't get stuck in traffic, but of course you have to schlep your bags into the RER stations (often no elevators or escalators; I'm not familiar with the station at Gare de Lyon). Air France buses (which can be used by anyone regardless of airline) go from Gare de Lyon to CDG. It runs every thirty minutes, and costs 17 euros per adult and 8.50 per child. http://tinyurl.com/y95s5c4 and scroll down for Line 4. Private shuttles often get bad reviews, but if you want one, search here and on other forums for advice before booking.

Air France bus #4 goes non-stop from Gare de Lyon to CDG. Buses run every 30 minutes. The fare is €17.00 if bought on the spot and €15.50 if bought in advance online. These are highway buses and your bags go in the luggage bay. If you're packing light, take the RER D from Gare de Lyon to Gare du Nord and the RER B from there to CDG. Be aware that the RER B line divides northeast of Paris so be sure to get on a train that is going to CDG. Train's run about every 10 minutes and the fare is €9.25.

After I posted my note, I saw that Harold had beaten me to the punch by one minute. I suggested taking the RER D to Gare du Nord rather than the RER A to Chatelet-Les Halles because Chatelet-Les Halles is a huge transportation hub. It's easier to transfer to the RER B at Gare du Nord.

Yes, Tim is right about taking RER D to Gare du Nord, instead of my route.

Thank you all for the help. After looking at all your instructions, the RER terrifies me!!! I'm taking the #4 bus. Seems simpler. My flight leaves at 11 am on a Friday so I will have to take the 7:30 am bus. Is an hour or so to the airport......I hope. Or perhaps 7 am is safer?
Thank you so much.

If you're flying home, you should be at CDG a full three hours before your flight's scheduled departure time. In that case, take the 07:00 bus.