The answer to this question is 18 rated due to sexual content. Please be mindful of this.
Answer – This is a very difficult question and depends very much on the reason for the infertility. I’m afraid if there is a serious medical reason for infertility spell craft will be unlikely to be much help. That isn’t to say it wouldn’t have an effect (depending on the severity of the medical issues of course – no amount of magic will help a woman who has had a hysterectomy to get pregnant…) but it will depend very much on the circumstances and it is by no means an exact science.
What I will caution you about is consulting a witch on a paying basis for fertility spells as this is one of the areas of magic that seems to be overpopulated with charletons. There are some very credible witches with genuine healing abilities but the chances of finding one among the pretenders looking to exploit grief and desperation are slim. My advice would be to take personal ownership for any spell work undertaken for this purpose or to avoid magical solutions altogether.
If you do decide to use magic to increase fertility then my best suggestion would be to link it to the birth and growth of something living. The best thing for this would be a plant that you can nurture from seed and using as a symbolic link for the idea of a seed taking root in your womb.
In your question you specifically refer to healing the person so I think it is important that you pay good attention to the environment you will be planting your seed working in as your prepared seed bed will represent the womb that needs nurturing and healing prior to the impregnation. Acquire the best quality soil you can buy and filter it gently through a sieve to get it as fine as possible. Place the soil into a pot and customise the pot as a personal representation (name written on it, buttons stuck on, ribbon tied round, anything that marks the pot as belonging to you). Don’t plant the seed straightaway, put your pot somewhere safe and warm and take it out a few times a day to hold and as you do visualise your desire for fertility infusing the soil. Build up a link with the pot and create a strong link between the environment you have created for your seed and the womb of the person hoping to conceive.
(Note you ask in your question about helping a loved one so you can either do this on their behalf and visualise the link between that person and your representation or explain to the person how to actualise the working themselves.)
Once you have built up the relationship with the representation of the womb it is time to plant the seed. If it was me I would do this as a ceremonial enacting of the sex act. I’d certainly suggest coating the seed with a mixture of your vaginal juices and his seminal fluid. (Either that or get your partner to ejaculate into the depression for the seed you have made in the prepared soil). This may sound a little icky but will reinforce the bond you are putting in place.
Once the seed is planted, cover it carefully and follow good gardening practises for germination (warm dark place until the seed sprouts and then move to a warm place with lots of natural light so the shoot flourishes). Think carefully about the seed you choose you use – don’t wreck the spell by planting a seed that is meant to be planted at a different type of year or in a specific type of soil or one which doesn’t like growing in containers. This time of year (Dec) is a good time to plant your winter pansies but you might want to have a look for something with more longevity – a tree seed perhaps – that you can nurture over a much longer period of time.
Keep the link going by holding the pot daily and reinforcing the bond between yourself and the plant that grows from your seed.