We present a powerful decision support system for bidding in simultaneous ascending auctions (SAA). Such auctions are commonly used for the allocation of spectrum licenses and electricity generation contracts. Our system can simulate the SAA under a variety of assumptions on the participating bidders and market conditions while it comprises a multitude of innovative features: a) a formal definition of bidding strategies for the user to choose from, including an original strategy that we propose, ii) means of incorporating a bidder's prior knowledge about market demand, iii) functionality for introducing beliefs about rival bidders' strategies, and iv) provision of on-line recommendation about the bids to be placed in a SAA in progress. We also present a set of experiments that corroborate the usefulness of our system.