out4trout, lots of good stuff so far but let me build a little on what TP said. With tongue in cheek he refers to the Crossfit warm-up as the workout before the workout - reason is for a lot of folks it is a workout all by itself.
I would actually suggest treating the warm-up as your workout for at least a couple weeks.
Start with 5 rounds of
5 pull-ups (jumping or beginner pull-ups if necessary)
5 press-ups (or push-ups for you Americans
)
5 sit-ups
5/5 lunges (walking or static)
10 squats
Push-ups emphasise keeping your body bosture static throughout the movement, no yoga-ing.
Depending on your issues, sit-ups may be a no go at the moment. If so, just leave them for a little while.
Lunges - nice long stride, get balanced on the front foot then let the rear knee bend and drop towards the floor. Let it kiss the floor gently then drive up out of the lunge using the front leg. Will help open up the hip-flexors as well as giving the legs some work.
Squats - download the air squat vids off CF.com and make sure you are doing them right. At present your major quality point is maintaiing the lumbar curve and not allowing your butt to tuck under at the bottom of the squat.
Once 5 rounds of 5 become EASY, increase to 5 rounds of 6. Rinse, lather and repeat.
This next point relates both to the warm-up above and further skill work below. What we are trying to do is avoid sending your back into spasm and sending you to bed for a few days. If in doubt, less is more and if the next morning brings no symptoms, sneak in a little more that day. Because of the relatively low intensity you should be able to do this everyday. A strategic withdrawal will let you live to train another day. Pay particular attention whenever you add a new drill into your mix.
Next step, buy yourself a 7’ length of PVC pipe or a broomstick and start working on your deadlift, squat and press form. Download all the vids on CF.com relating to these drills, watch them a couple times then attempt to imitate. Can be useful to have someone watch you and compare your form to that displayed in the vid. Even better, if you can video it and post it up so we can check it out.
Whilst unexciting, I would suggest that you stick with this level of intensity until you have the movements down and have your warm-up up to 5 rounds of 8 or so. We are laying a foundation for your future here. Don’t rush things!
Hit up this thread if you have any more questions.
Cheers, kempie