Based on the patterns described here, I've chosen three structures that looks better IMHO.
Suitable for medium to large-sized projects, uses a different stylesheet for every page.
Works best for designers, but is a good all-around solution for small to medium projects.
It may be an overkill for small projects, but you never know how big it's gonna get! if you stay positive you'd better be prepared.
Preboot is a comprehensive and flexible collection of LESS utilities, basic variables and mixins are ready to use, for more examples take a look at their documentation. Preboot is LESS based, but I've included mustangostang's port, so it's available in both versions of this structures.