Ok, I've done the 4 exercises Mark recommends, pushups, chinup, planks and squats.

I'm pathetic and only doing the beginer's ones.

I've done it twice now with lots of rest between. (days)

I can only do 30 wall pushs, 20 2 legged assist chinups, 35 squats(full ones) and 75 sec plank on my knees.

Should I be doing these every other day, every 3rd day etc etc to build myself up?

Any advice I should be doing to get better at it would be most greatly appreciated.