In the past, the RATP bus checkers were easily identifiable in their RATP uniforms. Those who were planning not to pay the fare simply did not get on the bus or got off as the checkers were getting on. This morning two very hip looking young men, probably in their early twenties, got on my bus. After the bus started they flashed their badges and proceeded to check tickets. By the time the next stop came, one positioned himself in front of the bus and one in the middle. Sure enough, a young man ascended and simply passed by the ticket machine. The checher on the front of the bus gave a signal to his buddy and the violator was toast. It all went down very quietly and I doubt if many others noticed or cared. Sort of fun to watch!

I am sorry if this sound really stupid. I have no idea of what you do when you get on the bus. Let’s say I have carnet tickets, do I have to push them through a machine, pretty much like I would at the metro?

If I have a carte orange or mobilis, do I just show it to the bus driver?

This question is really bad. When I get on the bus, am I expected to leave through the back door or can I also use the front?

I won’t be able to use the metro this time and I am stressing out about simple things that I would have never considered before.

If you have a Carte Orange or a Mobilis ticket, or a senior pass, just show it to the bus driver. Some of the more seasoned Parisians do not do this, but if they are checked they hace their passes. By the way, you should write your Carte Orange number (the number on the orange ticket with your picture) on your ticket when you purchase it. This is a safeguard against sharing.
If you by a carnet or an individual ticket from the driver, there is a ticket machine just to the left of the diver. Put your ticket in the machine and it will be stamped with time and date and returned to you. Have it handy for a checker and you will not have a problem

Use the front door. Carnet tickets go through a little machine. Carte Orange or Moblis you show to the driver. There are buttons to push to signal when you want to get off. Look for "le Bus" by L'Indispensible, very handy guide to the system and the individual routes.

Thanks for your help on "the basics". I feel better now.

On a double (or a triple!) bus you may enter through one of the rear doors. There are ticket machines there as well. Many Carte Orange and Mobilis holders enter through rear doors as well. Much more convenient during rush hour crowds.

and if you'll be boarding with a baby stroller, you can board in the middle and park the stroller in the open area (no seats). then stick ticket in the box to stamp it.

a Paris Visite pass and a Carte Orange pass have tickets, too, but do NOT stick those in the box on the bus - it will cancel them for further use.

I believe the Mobilis tickets says right on it that it is supposed to be composted in the machine, just like a regular single ticket. I have no idea why, but I always do because it says that. It doesn't ruin them (like I guess it does for a Carte Orange? never did that), as I've done it.

As I said, I don't know why it says that but I just do it to follow the rules. I wondered if they could actually keep track by the machine of when you are using your Mobilis just for research purposes, but kind of doubted it. I have one right on me now and it says on the back "introduisez votre ticket dans les appareils de controle sur les reseaux ferres et bus".