There are so many ways you can make your toiletries go further that I couldn't possibly list them all. So I'm just going to give you a few of my favourite ideas that I've tried and tested that really work.
When using shower gel apply it to a puff, you only need about a teaspoon full and you'll be able to wash your whole body with it. Puffs are also great to use with bars of soap as they lather up very quickly. If you're one of those people that uses a sponge or your hand to wash yourself then you can make your shower gel last longer by using one of those foam soap dispensers like you find in some public toilets. Just simply add 2-3 tablespoons of your favourite liquid soap to the bottle and top with water. This dispenser is also fantastic with hand soap and especially good when you've got kids as it lasts a lot longer and is less messy. The days of hand soap all over the sink and a bottle only lasting a week or so is now a distant memory!
When you're on the last drop of shower gel or shampoo, add a little bit of water to it and give the bottle a good shake to loosen any stuck to inside of bottle. You should be able to get another couple of uses out of it before throwing the bottle away. With hand wash you can add more water, again give it a good shake to mix it up. Don't worry about the bubbles as they will settle. What I also do with the last dregs of shower gel is use it to make bubbles in my daughters bath. She also loves playing with the empty bottle!
Watch how much shampoo and conditioner you use. A tablespoon is generally enough for someone with mid length hair, use less if you have really short hair. When you've got to the end of the bottle, turn it upside down to let the last few drops settle in the top so that when you next use it the last drop will come out very easily. Also, you don't need to wash your hair every day, you are stripping the oils by doing so. I have long hair and wash my hair 2-3 times a week and it never looks dull or greasy! Also, don't use conditioner every time you wash your hair as this can cause the oils to build up. If you don't mind diluting your shower gel or shampoo, top it up with water when you're about half way through and give it a good shake. If you don't like the idea of using it very diluted just add a little water to make it stretch a bit further than usual. Shampoo that's more diluted will cover your hair more easily and lather up quicker, plus you'll also be using less.