Snakes develop habits in their feeding. They get used to a specific type of food. It can be difficult to change these habits. Check with the pet store or previous owner to find out what the snake is used to eating.
The rate of growth in your snake will depend on what and how often it is fed. Some say it is better to offer several small items rather than one large one. If you feed your snake an item that is too big it may be regurgitated (yuck). A good rule to follow is the prey should be no wider than the snake at its thickest point.
How frequently your snake eats will depend on a number of factors. Some may eat twice a week. Others may only eat once or twice every two weeks. Food should be offered at least once a week. More if you are feeding small items. Be careful not to over do it. A snake that is offered too much food can become obese and lethargic. It is extremely difficult to get rid of excess weight. If you feed your snake too little it can become aggressive and/or health problems can occur. Remember problems in a snake may take a while to notice so be sure to get on the right track as soon as possible.
Now the debate over live or pre-killed prey. Live prey can be a hazard to your snake (I know it sounds silly). Any rodent is more intelligent than any snake out there. Anyone with a Ball Python can tell you that a snake can be intimidated by an aggressive rodent. Despite all of this, I prefer live food for my snakes. It is interesting to watch and I feel it gives the snake some connection with it's instincts. If you choose live food always keep an eye on it to make sure it doesn't become aggressive. If it is remove it. Kill it and try to feed it to your snake killed. A safe and humane way of killing a small rodent is to place it in an old sock and smack it on a table. Use enough force to kill. It can take a lot. There is also the option of stunning the prey but, this is difficult to describe and can also be difficult to do.
Now for pre-killed (or recently killed) prey. This is the safest route to take. However, it can be difficult to get some snakes to eat pre-killed prey. For smaller snakes you can use a pair of long tongs or forceps to wiggle the prey in front of the snake. This usually is enough to fool the snake into thinking it is alive. Do not do this with large snakes.
Whether live or pre-killed prey is offered sometimes a snake will refuse to eat. After the prey has been introduced, wait for an hour. If the snake does not eat it try again another day. The reason may be that it is going into a shed and will not eat during this time. There are times when some snakes go through long periods without eating. This may be a sign of illness, poor environment, or a gravid snake. Be sure the temperature and humidity are at the appropriate levels before doing any thing else. Inspect the snake for signs that it is gravid or ill. Your veterinarian can help determine these things if you are unsure. Some snakes just stop eating for no reason. There is nothing wrong with them or the environment. They just don't want to eat. Don't worry they'll come around.
A snake can go several weeks or even months without feeding with no
ill effects. But, any trend should be stopped as soon as possible. Just
keep trying and get some advice from a vet.