Read the Guides
http://guides.macrumors.com/Understanding_Intel_Mac_RAM
http://guides.macrumors.com/Buying_RAM
Assuming it is an intel Mini:
1. you will need to buy a matched pair (if you want 1GB of RAM total, you need to buy two 512MB sticks, 2GB total would be two 1GB sticks)
Incorrect. The Mini, as with all intel Macs, will work just fine with one SODIMM, or with mismatched SODIMMs. You gain about 6% - 8% in performance by having matched RAM. But that is a poor reason to go and buy a 512 Mb module just to match another 512. Its better to have MORE RAM then Matched RAM.
2. it needs to be PC2-5300 RAM
True, but only as far as it goes. It's like saying your tires have to be 15" (and forgetting to mention the width or profile)
The RAM has to be PC2-5300 DDR2-667 MHz 200 pin
SODIMMs. 240 pin desktop sized PC2-5300 DDR2 667 Mhz DIMMs will not work.
OP: The Apple RAM you linked to is the wrong RAM. Its a 533 MHz DIMM, not a 667 MHz SODIMM.
Also, when asking for help, please specify exactly which model of machine you have. The G4 Mini uses totally different RAM from the intel Mini. Lastly, posting your email address on a forum basically guarantees you're going to get tons of spam. You may want to edit your post and take it out. Contact a Mod (Contact Us at the very bottom of the page) for help if you can't edit.
My recommendation to the original poster, and anyone who is not really familiar with the hardware, is to purchase from a reputable seller who knows Macs, will offer a guarantee of compatibility with your model Mac, gives a lifetime warranty, and offers a no charge (no shipping, no restocking fee) return for replacement or refund if it doesn't work.
Data Memory Systems and OWC are two vendords that know Macs and are often recommended here.
