Whats the best technique for welding plates in floor of a car? Ive put a couple in but i think my welding cud be betta,sometimes it dosent seem to take and then sometimes it just puts a hole in the floor!

Should it be welded from both sides?or should the weld go all the way through the metal? Also what settings would u use on the welder im using a 150 amp gas mig welder with 0.6mm wire!

I know it would be easier to get a proffessional but time and the fact i wanna do this myself,just so i know i can!

Thanks...