Once your newly born kittens get to about four weeks old, they will be ready to start weaning onto solid food. Their mother's own bowls of food will be far too rich for them, and you will need to encourage them onto solid food such as human baby rice or cereal mixed with a touch of evaporated milk and a little warm water to heat it up. You could also try pilchards (with any trace of bones removed) mashed up with warm water - the stronger smell will sometimes get them interested. Make sure that your queen does not eat the kittens' food until you are sure that they have had enough.
At first the kittens will be a little confused about what they are supposed to do with this new substance put before them and will paddle in it and generally make quite a mess, and may even try and eat their cat litter instead, but it won't take very long before they get the hang of it. Your queen will also see to it that the kittens are litter trained as soon as possible after they go on to solid food, as she will not want her bed to be soiled. There may be one or two minor 'accidents' to start with, but she will litter train them by placing them onto the litter tray when they have fed.
Gradually the kittens will become more interested in what their Mum is eating, rather than the special baby food, although they will still enjoy the comfort of feeding from her from time to time, probably up until almost the time that they are old enough to leave home. There are a lot proprietary brands of cat food formulated especially for small kittens that are easily digested in tiny stomachs. As time goes on and the kittens are less reliant on their Mum for food, your queen will want some time away from them and will welcome the opportunity to enjoy the company of her old playmates. Some queens are happy to share babysitting duties with other cats in the household though they may become very protective if the others take too much interest in her family.
You will quite probably need to take precautions to make your home kitten-proof as soon as they become more mobile and start exploring wider afield. If they have been confined upstairs, as soon as you allow them out of their feline nursery make sure that they cannot fall down the stairs, through the banisters, or even into a human toilet or full bath - it is essential to keep the toilet seat down when you have small kittens about. You will also need to make sure that they do not start chewing TV wires or investigating the washing machine, an open fridge door or a flip-top rubbish bin - if you have never had a litter of kittens before you will be amazed at what they can get up to, and where they fall asleep.
You will obviously need to know which of your kittens are male and which female before you can think about registering them - you may need to get the help of your queen's breeder or the stud owner if they are local to you, or if not, hopefully you will have made contact with other, more experienced, breeders who can help sex your new kittens. If not - you will need to ask your vet, and make sure you get them to explain it to you so that you will know for next time! Depending on the breed you have, and the possible colour combinations, you may also need advice on exactly what colours you have in your new litter. If you have already registered a breeding prefix, you will be able to use that to register your new kittens when they are about 6-8 weeks old, otherwise they will be allocated an 'administrative' prefix if you register your kittens with the GCCF. It is very important that your kittens are registered, even if they are not going to be shown or bred from, as you should not sell kittens as 'Pedigree' unless they have a full set of registration papers. You should also prepare a signed paper pedigree for each kitten.
Invite prospective new owners to your home to look at the kittens with their mother, once they are old enough. It is acceptable to ask for a non-refundable deposit, to make sure that the people visiting are genuinely interested in having one of your kittens - and you can then take that off the final cost of the kitten. The GCCF recommends that new kittens should not go to their new homes before they are 13 weeks old, and before that, you must have them vaccinated - the first jab when they are 9-10 weeks old, and the second at around 12 weeks, making sure you allow a few days before they go to their news homes in the unlikely event that they react adversely to the vaccine.
When your kittens are ready to leave home, new owners always appreciate it if you have compiled a wallet with all the papers - pedigree, vaccination certificate, a suggested diet sheet, the registration document ready for the new owner to transfer ownership, and a receipt. You might also set up an insurance policy that some companies produce that will cover the kittens for the first 4 weeks in their new home, and then encourage the new owners to either renew it or take out an alternative policy at the end of that time. It's also nice to include a toy that the kittens have enjoyed playing with, together with a sachet or two of their favourite food to help them settle in.
Invite the new owners to contact you to let you know how their new addition is settling in, and make sure that they know that if for some unforeseen reason the new home does not work out, you will help by having the kitten back, or assisting with re-homing if there are problems when the kitten becomes a cat. Reassure them that you are available if they have any queries, and hopefully you will set up a good rapport, and receive photos and progress reports for many years to come.