1.  Pressure wash fence surface leaving ample drying time prior to staining.
2.  Stain surface with two coats of oil base or acrylic stain.
While many coatings claim superior life and color retention, we recommend using an oil base product if you are trying to achieve a brighter, more natural looking surface.
Want a longer lasting coating?
Use an acrylic product if you are willing to compromise some clarity of wood grain.
Life of a typical oil-base coating in full sun – 1 to 2 years.
Life of a superior acrylic-base coating in full sun – 3 to 4 years.
Surface durability will vary given ultra-violet exposure.

Manufactures tip #1 -

When choosing an oil-base product, wet on wet coats are required.
When choosing an acrylic-based product, ample drying time in between coats is required.