When to stain new fence?

The answer will depend on the type of fence you have erected and your personal taste.

The most common reason for staining a fence is two-fold, esthetics (the look of the thing) and preservation (stain helps to extend the life of some types of wood).

For un-treated wood (except cedar) you can and in most areas should stain your fence immediately you finish putting it up.
Semi-transparency or solid, latex/acrylic or oil based stains all work and have various pros and cons.

For cedar fences, personal taste is your best guide. This is one of the woods where preservation is less needed. Teak and cypress being two others (but the prices for these can be prohibitive).
Good cedar will "silver" within a year or two, depending on your area, and the amount of "weather" you experience. If you like the look of silvered cedar, it is completely un-necessary to do anything but wait.
If, however, you do not like the "silvered" look, the fence will need to be stained, usually after the first year.

Pressure treated wood should be allowed to weather a bit before staining. It usually comes with a bit of colour from the chemicals used in the process, so it is best to let that fade, particularly if you are using a semi-transparent stain.
Depending on your area and the amount of "weather" you get this will take anywhere from 2 months to a year.
Once the wood has started to grey give it a good cleaning, allow to dry and apply your stain.
If you are using a solid stain, the timing is less important, you can usually paint it with a solid stain within weeks of finishing your project.
The answer will depend on the type of fence you have erected and your personal taste.

The most common reason for staining a fence is two-fold, esthetics (the look of the thing) and preservation (stain helps to extend the life of some types of wood).

For un-treated wood (except cedar) you can and in most areas should stain your fence immediately you finish putting it up.
Semi-transparency or solid, latex/acrylic or oil based stains all work and have various pros and cons.

For cedar fences, personal taste is your best guide. This is one of the woods where preservation is less needed. Teak and cypress being two others (but the prices for these can be prohibitive).
Good cedar will "silver" within a year or two, depending on your area, and the amount of "weather" you experience. If you like the look of silvered cedar, it is completely un-necessary to do anything but wait.
If, however, you do not like the "silvered" look, the fence will need to be stained, usually after the first year.

Pressure treated wood should be allowed to weather a bit before staining. It usually comes with a bit of colour from the chemicals used in the process, so it is best to let that fade, particularly if you are using a semi-transparent stain.
Depending on your area and the amount of "weather" you get this will take anywhere from 2 months to a year.
Once the wood has started to grey give it a good cleaning, allow to dry and apply your stain.
If you are using a solid stain, the timing is less important, you can usually paint it with a solid stain within weeks of finishing your project.