Northstar is right, what is your preference? Are you trying to setup a DSB (deep sand bed), or are you just going for the typical 1-2 inch thick sand bed.
Benefits of a DSB:
1. A must if you are going to house sand sifting critters, ie. gobies, pistol shrimp, some star fish, horshoe crabs, etc.
2. More importantly, a DSB provides a medium for anearobic nitrifying bacteria, which is extremely beneficial in helping to keep nitrate levels down. Many mature tanks often suffer from higher than normal nitrate levels because of feeding, dead spots in water circulation, etc. A DSB can help combat that.
If you want a DSB, then you need a lot more than 1-2 lbs per gallon, you will probably need something closer to 4 to 6 lbs per gallon. There is a simple rule to help, 1 pound of sand per gallon, this is a guideline, there is a better ratio, but I don't remember what it is at the moment, there is a ratio that takes into consideration the actual square footage of your tank, which is better if you have a non-standard sized tank.
Good luck.