Drywall, as well as insulation and electric are other items for which you will probably not be able to save much as well since pricing is standard and these services are widely used.
Where you can begin to save money is in doors and windows. There are many discount stores as well as salvage places that carry a wide variety of designs. If you have a place to store these items, and you are not limited by design, this is the first step in achieving savings.
Plumbing fixtures are a great way to save money. However, you will need to know up front what fixtures will go in showers and tubs as these require valves installed up front during construction. It is also important to consider warranty when purchasing these items. You want to be able to return them, or receive defective parts from your vendor if the need arises.
Electrical fixtures are also constantly on sale. You can purchase these from the Internet and local stores. Keep in mind when purchasing lamps, chandeliers, fans, etc, their size, location of the electrical contact so you do not purchase an item that will not fit, or is too heavy for the framing and makes you incur costly change orders.
Tile offers a great opportunity for savings. Depending on the look you want to achieve, you can select a tile that is not very expensive for the main part of your shower and splurge on accents. Most people focus on the overall design and do not focus on the background. Still, keep in mind, proper installation of tile is important for presentation, no matter the price of the tile you've purchased.
On landscaping there are easy ways to save. If you do not mind waiting a bit for your landscaping to look "finished," you can order smaller size plants and allow them time to bloom. Usually prices for smaller plants are less and really you only need to wait a month or two for a full landscape. Just make sure you give your plants proper irrigation.
Lastly, allow for future improvements. There may be many features you want to incorporate in your new home/remodel. The trick is to do them all correctly. Trying to cut corners on finish outs or quality in order to save money or cram an entire wish list is not a smart move. Quality is important. Discuss with your builder and decide what items can be left for a "second phase" without affecting cost in a big way.