Not enough information. Tactics depend on various factors:

(1) the venue, since auction formats differ greatly across domain market places;

(2) which of various auction types at a given website you're looking at;

(3) listing settings decided by the seller such as "buy now" options or a minimum reserve;

(4) the seller's past habits with regard to promoting, altering, or even -- unfortunately -- rigging auctions;

(5) Quality of the domain itself relative to the price.

Without knowing the details, no general answer that applies to all situations can be given.