The most cost effective waterproofing I have found is cold spray-on modified asphalt on the outside of the wall with a footing drain to lower ground. But if it is not usually done in your area you might have to search for an installer. Don't settle for trowel-on "damproofing"; it is worthless.

Don't forget to add the corrugated sheet materials to the outside of the block before back-filling. It will provide a way for water in the soil to reach the footing drain pipe without forcing it into the waterproofing and block material due to hydrostatic pressure.

Thereafter, ensure that surface water drains positively away from the foundations, including all roof downspouts and roof run-offs.

Depending on the amount of water normally in the soil and the amount of annual rainfall, a basement sump pump provides extra insurance for any water that get into the basement interior.

Good luck!

Have they already built the foundation? You may want to consider a poured concrete foundation. It has less porous surface area than the mortar material used with blocks.

-poured concrete foundation definitely helps
-roll on or spray on damp proofing
-over damp proofing install water proofing membrane product, see link
-then drain tile around foundation at footing level, no over footing at wall junction
-if you're on a hill, try draining your draintile to daylight instead of sump
-finally, washed clear crush gravel back fill

Here is a link that might be useful: water proofing

There are a number of steps to a proper basement, most of which have already been mentioned. First, I believe a perimeter drain system is now code. This is perforated pipe or some other product down at the bottom to collect water, which either drains away naturally if you are on a hill, or is removed with a sump pump. Waterproofing the foundation itself usually consists of a membrane, either brush/roll-on, or peel and stick. This membrane should be protected with a dimple or drain board, which facilitates drainage rather than allowing the water to remain trapped against the wall. Ideally, the hole should be backfilled with gravel most of the way up. The gravel is covered with geotextile to keep dirt from clogging it, and then covered with a layer of topsoil. It is important to correctly grade the soil to drain water away from the foundation, and lastly, you should have roof gutters to divert the water on the roof away from the foundation.

Sound like a lot? Despite all of this, the basement may still be damp, due to condensation on the cool walls in hot, humid weather. Insulating the walls, preferably on the outside, will help this.

Don't confuse dampproofing with waterproofing. Damproofing is not intended to be waterproof only water resistant. It will resist light water pressure against the foundation for a limited period of time so it is virtually useless and rarely specified since the 60's. It would not be used in conjunction with a waterproofing system.