Watch out for paving sands that may have binder additives. I'm using well washed pool filter sand and am happy with it. You also want to be careful with some sands as very fine sands can pack badly which may inhibit the development of a good substrate eco-system. Many have used basic play sand with success.
The key to using any sand is washing well to remove 'fines'. Fines are the small dust like particles of sand that result in cloudy water. As others report, the best way is to use a 5g pail and a garden hose outside. Place an amount of sand about 1/4 of the 5g pail, add water with force, stir and pour off the top. Repeat until the water coming off is clear.
If your tank is new, just add the washed sand, fill part way with water, plant and 'sea-scape', then fill with water. If your tank is established with gravel, you should remove a sufficient quantity of water, remove the stock and decor, then remove the gravel. I found that a scoop made for kitty litter worked really well for removing the gravel with the last little bits being removed with a fish net. Then add the sand, sloping rear to front, add the plants and decor, after the tank has settled, add the stock back and refill the tank to full.
I have come to believe that an undisturbed [deep] sand (approximately 3" or more) substrate is better than gravel in many ways. It is too easy for uneaten food and detritus to get too deep in gravel too quickly. Gravel really requires routine gravel siphoning to keep it from becoming a 'nitrate factory'. On the other hand, with sand, mulm forms on the surface of the sand where it very slowly decomposes. In excess, this material can be much more easily removed from the surface of the substrate by merely hovering a siphon above the surface. HOWEVER, mulm is a very healthy thing to feed the bacteria in the substrate and convert the material into usable plant food so unless it becomes excessively unsightly or offensive, it is best left alone.
Further enriching the sand substrate is another consideration. The addition of Malaysian Trumpet Snails and California Black Worms serve to aerate and assist in decomposition of mulm. In addition, the worms provide a natural live food source.
Note: Black worms may require periodic restocking as they are aggressively hunted by stock.
Well enough rambling on about sand. Good luck in switching to sand. As most report, you will most likely be glad you switched.