For the original cartridges, soft resetting shouldn't hurt it (just don't soft reset while you're saving)
that's if you're playing on an original cartridge.
Counterfeit cartridges and some piracy-romloader cartridges uses a battery to store the save.
I bought a pseudo Emerald cartridge (It's a Japanese -> English bad translation fake cart) while waiting for Emerald to be localized, and when the battery died I lost my save and any capability to retain saves.
Still, I could do trades and keep my progress, as long as my GBA SP remained on and charged XD
There are youtube videos that will help you.
To get started, you're gonna need
1. the common trade Pokemon (as described in the video),
2. a way to clone said Pokemon
3. A way to perform the Pomeg Glitch.