Ramps are the safest for sure. You can get REALLY solid plastic ramps @ any Advance Auto / Auto Zone / Etc for like $30-40. Once the car is on the ramps, it would take an act of god to get it knocked off.
I'm glad you at least asked before posting a picture on the web of you working under the car only supported by the scissor jack... I can't tell you how many times I've seen that. Scary crap... THAT is a dumb idea.
The ones I got are 8000 lb (total) ramps:
http://shop.advanceautoparts.com/we...cle-Ramps-Blitz_9040020-P_N3400_T|GRP2042____
These EASILY will hold my pathfinder, that I use to tow the Miata.... that is to say that they also work with my Miata, my VW Jetta and my old Protege just fine lol.
Cheap, CHEAP life insurance if you know what I mean
For basic maintenance these are fine.
For more intensive stuff, suspension work, clutch changes, etc etc, you want something that will safely get the car up higher. I have a couple sets of REALLY stout jack-stands that I use for that (WAY over-rated for my 1750 lb miata lol) that work great. I just take GREAT care when getting the car dropped down on them to make sure the car is sitting right on them, and to make sure they are sitting right on the floor.