So a little while ago, my mum was doing some home renovations and I pretty much (with little experience) ended up planning her entire kitchen design for her! 
Her kitchen is medium sized and a very practical space (she loves to cook) and I amazed myself by how much I enjoyed researching and designing a space for her. 

It was SO important to find a good reputable builder and a trustworthy supplier, someone with a large range who would provide a good service – somewhere like Kitchen Warehouse which allows you to build a custom space.  

So here are some steps I took in designing her kitchen:
1. Decide what you need, what you don?t 
Duh, this is obvious right"  But sometimes there is dead space (for example my mum had some cupboards in a weird position that she never ever used) so we decided to use some pull out drawers which would make it easier to access things.   She did not have a dishwasher, so we decided to add one of those and a built in microwave to save tabletop space. 
2. Pinterest
I found Pinterest really useful for finding inspirational images. Even though some may not seem to fit perfectly, you can take some design ideas, such as for paint or tiles. There are also kitchen magazines you can buy if you prefer a paper copy. 
3. Budgeting
The obvious one.  Kitchens can vary in price but you will expect to spend a few thousand pounds on one.  Adding everything up will help you decide what appliances, Kitchen Units, decorations etc. you can afford....