I am using the Geil® Value 1Gb PC3200 Dual Chan DDR Kit (2x512MB) (Cas 2.5 6-3-3) for the options and reasons that I chose this see here.
As with the CPU I think its good to avoid touching the metal parts, specially the pins, with fingers. Also be careful to discharge any possible static.
The number of pins is different on each side is different, so make sure the memory is the right way round.
I'm not sure if I did this correctly, I opened the white catches at each end, then pushed down on the memory. Even with quite a lot of force the memory did not go into its socket, then when it did it went in at one end so then I pushed the other end in. I think that I should have used the white catches to provide additional leverage, then perhaps the memory would have gone straight in.
Then insert the second memory card into the black socket.