Tip1. Adhere a used film leader to a new roll of film
When you load your film inside the camera, the film leader is wasted because it has been exposed to light. So for every roll of film, you will waste at least this much, which is a pity.
But if you adhere a used film leader to a new roll of film, you will be able to have at least 2 more exposures.
A similar method is to load film inside a darkroom changing bag, so the film leader would not be contaminated by light. You will also have 2 bonus exposures per roll.
Tip2. Bulk-loading
If you shoot black and white film, bulk-loading is a great way to save money. Basically, you buy a reel of film (100ft, 400ft, or 1,000ft), and put them into 35mm canister. That is bulk-loading. Usually, 100ft can be loaded into 18 rolls (36EXP). A roll of Fomapan400 is being sold at US$5-6 as of today, but if you do bulk-loading, each roll will cost you about $3. You do have to invest in some equipment to do bulk-loading though. You mainly need a bulk loader and a changing bag (you can utilize your used canisters). In total, they will cost you no more than $100.
If you shoot color film, the only option for bulk-loading is Kodak motion picture film. The average cost of each roll (36exp) is about $5, whereas a legit Kodak color film is more than $12. But motion picture film requires the ECN-2 development process, which is not available everywhere. If any, the development fee is much more expensive than C-41, the process needed for ordinary color negative film. So if you shoot color film, bulk-loading would not save you money unless you develop film at home.
Tip3. Avoid wasting your film
When you shot a roll of film, some images turn out great, while the others do not. If you can improve the probability of taking great images, you also save money. There are something you can do to avoid taking bad images. For instance, don't shoot color film in cloudy days, when you cannot maximize the performance of color film. Also, avoid using cameras that have faulty auto focus. Auto focus is not always accurate. If you find your camera does not focus very accurately, stop using it. Instead, use a camera that allows you to focus manually, and focus carefully each time you take an image.
Don't shoot film in cloudy day
Make sure each image is properly exposed
Don't use cameras that can't auto focus well
Some very useful advice here. Please let us have more of your suggestions!