Just be careful to put the card in the right slot - I have seen novices put the card in the money slot and lose it. If not sure, ask the bus driver (or watch the people in front of you). Remember that the difference between the Chicago Card and the transit card is that you can go 'negative' on you Chicago card but not on the transit card - not enough money on the transit card and you cannot board.

Also, if you are not used to riding the bus, a couple of things for courtesy - have your fare (cash, transit card, Chicago Card) ready when you board the bus, don't fumble once you get on to find the fare - also move to the back of the bus if it is standing room only. Seats are not for packages/suitcases - so if the bus is getting crowded, move them off the seat for another passenger.

I think that people are afraid to use the bus but I use it in conjunction with the L everyday and it is pretty efficient and gets you where you want to go.