Basements: If you are looking to seal your basement floor look for a penetrating waterproofing sealer that will reduce hydrostatic pressure and vapor transmission. Do not use an epoxy, acrylic or latex based sealer that will peel, flake and delaminate at the first sign of water. If you are looking to seal concrete block walls or cinderblocks use a silane/siloxane blended sealer to fill the pores of the extremely porous blocks.
Patios: If you are looking to seal your patio of pavers look for a non-yellowing acrylic sealer; one that will hold up to wind driven rain and UV light. Acrylics are extremely common sealers with every manufacturer offering their version of an acrylic. Look for an industrial grade formulation, they might be pricier but they will last longer than a garden variety sealer. Acrylics are available in high gloss or a low sheen, solvent based and water based respectively. Water based versions are excellent for their low VOCs while solvent based acrylics will last a little longer.
Driveways: Look for a penetrating silane/siloxane sealer that will hold up to water, and salt degradation. Used by the Department of Transportation on all bridges and roadways, silane/siloxanes are excellent choices. Look for a silane/siloxane with a high percentage of solids since they will last longer and provide better protection.
Garages: The best garage sealers are epoxies and/or urethanes that are cyclo-aliphatic and aliphatic respectively. With these durable coatings oil and fluids have no chance to penetrate and they are easily cleaned up. Long lasting, look for a coating that will resist hot tire pickup.
Floors: For interior floors and warehouse floors look for a concrete silicate densifier that will create a smooth look after polishing. Lithium silicates are more reliable densifiers especially for densifying, hardening and increasing compressive strength.