Some just don't make it for various reasons. Education is the key to compassion with effectiveness. Animals that spend their lives serving man should not be discarded like so much surplus office furniture when they are no longer economically useful. Adoption fees are usually rather high because of the multiple expenses of food, diet supplements, medicines, veterinary care, and licensing fees. Joining with select others to pay a year's upkeep of an animal.
Sponsorships are much more affordable and also make great class projects for a school.
A non-designated gift of cash to a sanctuary offers them the most flexibility in using the resources where they are needed most. Such gifts may be lump sum payments or a trust fund. You need to seek the advice of a lawyer in planning a bequest. Volunteers do all sorts of work from unskilled labor to highly technical animal work and serving in board positions. What volunteers are allowed to do varies from facility to facility and even from person to person based on your background, strengths, and willingness to learn.