In block walls, cracks tend to follow the mortar joints. In poured walls, they can be anywhere. Cracks are usually of little concern if they’ve stopped moving. The National Association of Home Builders (NAHB) has established criteria for acceptable cracking in order to lessen the friction that can arise between homeowners and builders. In block walls, cracks up to 1/4-in. wide are acceptable; larger cracks must be addressed by the builder. Cracks in concrete walls must not allow water to leak into the basement.
Observe cracks over time to see if they’re active or stable. If a crack is still moving, look for the cause. Perhaps a tree growing too close to the foundation is putting pressure on the wall. Or, more commonly, there is water pressure against the wall, and either the water pressure alone, or a cycle of freezing and thawing, or both, is moving the wall. Fix the problem before doing anything else. Simply clean and caulk stable cracks. This will eliminate some seepage and keep out bugs.