How are trips assigned? Is it seniority or credit-balanced/first in-first out?

At my current airline a pairing is assigned to the most junior pilot who is legal and available, unless a senior pilot preferenced "call me first". Only after a reserve has accumulated credit to min guarantee do they start assigning based on credit.

Also, it sounds like if you live local and don't want to work the method is to bid short call. Is that correct?