Firstly I use only SanDisk or Lexar cards. SanDisk was the company that first introduced compact flash cards and is still an industry leader. Lexar has a reputation of being very high quality because of it’s professional line which has a lifetime warranty. I use both brands interchangeably, and both have been very reliable for me. I choose their faster cards which read and write faster and cost a bit more.
When choosing a card, buy the fastest one you can afford. Sandisk’s cards get faster with every ‘series’ they put out: Ultra II, Ultra III, Ultra IV. Lexar lists their speed as 80x, 133x, 300x, that is how fast they write compared to the original compact flash card specifications. Most cameras can’t use all of the speed the card can handle, but what if you upgrade your camera? Also cards that write faster usually can read faster, meaning that downloading your photos to your computer are faster as well.
Many people say that you should not delete photos from your card one at a time. I have never had any trouble, and I do it all the time. At baseball tournament I have to shoot