Formal:
* Choose
* Pick
* Elect
* Designate
* Nominate
* Prefer
* Opt for
Informal:
* Pick out
* Handpick
* Single out
* Go for
* Settle on
More specific:
* Cull: To carefully choose a small number from a larger group.
* Screen: To examine or test to determine suitability.
* Filter: To remove unwanted items or elements.
* Curate: To select and organize items for a specific purpose.
* Prioritize: To rank items in order of importance.
The best synonym for "select" will depend on the specific situation.
For example, if you are talking about choosing a winner from a group of contestants, you might use "elect" or "designate." If you are talking about choosing a particular item from a store, you might use "pick" or "pick out."