Rest Spots

Normal rest rules are too forgiving - many parties don't go through 4 or 5 'hard' encounters per day, but instead hoard their resources and come at every major encounter fully-loaded. So:

A short rest allows PCs to recover hp by rolling their HD, and to pick one class ability to refresh (that normally refreshes on a short rest).

*Or restore 1/2 your uses, rounded up, of short-rest abilities (like if you have 5 uses of Bardic Inspiration, recover 3; etc.).

A long rest does not automatically top up hp, you instead regain 1/2 your level (rounded up) of your spent HD, plus anything you regain through magical healing and healing kits and the like. You also refresh all of your short rest and long rest abilities.

*If you're playing with power points, restore 1/2 power points, or even allow mages to roll their HD and restore power points that way, choosing between hp and pp.

This helps balance out casters vs martial characters, and grants actual use to the Healer feat and to the Song of Rest ability.

However: there are places called rest spots that make rests easier or quicker. A rest spot is somewhere comfortable, safe, and refreshing that PCs can use to take a short rest in a shorter time. This might be a local all-night diner with the best coffee in town that allows a short rest in 10 minutes; a god's forgotten shrine deep underground that allows a short rest in 1 minute; or even the sight of an ally on the battlefield as characters get their breath for 1 minute.

Larger rest spots - inns, a home base, a brothel - allow PCs to gain back all of their HD after a long rest instead of half. Getting the 'deluxe' treatment there (spending some kind of resources) grants the well-rested condition (SEE: House Rule: Well-Rested).