There are a couple of ways for this (and more). One, you can create a generic Data Access Object (DAO) class and have one for each persisted entity (or as needed).
If you are applying Domain Driven Design principles, you would be using a Repository to access your database and this would be further simplified by the notion of Aggregates. Then you can have a generic Repository<T> (if you are using .NET 2.0 that generalizes all your CRUD functions.
Check out the Hibernate in Action book for their thoughts on access to the ORM and also check out
http://www.codeproject.com/aspnet/NHibernateBestPractices.asp for a decent example of a DAO.
Swing by domaindrivendesign.org for DDD stuff, too.