Depends what I'm doing. Most of the time I just crawl under there since I'm so skinny

Otherwise I break out ramps

yup, those are the ones I always used for my Bonne or my sister'* SSE and my sis in law'* L200. But with my Jeeps I don't need to jack them up unless it'* somthing the tires have to come off for :P

I can get under without jacks for the oil changes but for major stuff I got a lift at the shop

Block the back wheels,jack that sucker up and use a set of Redneck Jack Stands

Are those cinder blocks safe? No worries about sudden collapse?

How do y'all do it? I'm about as skinny as they come and I can't move under my car!?!

I've changed my oil without jacking the car up, and you're skinnier than me.

They're solid blocks. The bottom 2 just look like a cinder block

Forgive my caution, My father drilled it into my head very young to check, recheck and check again how secure the car is before putting anything, especially yourself, under it. Even today, if he comes over while I'm undercar, he will wait till I'm out from under, and give it a vigorous shake

Another safety note:
When using ramps, always block the rear wheels.
Sort of obvious, but worth pointing out!

I prefer ramps for oil changes. They are long enough to fit under my low car, just barely!

Adam