1. Plan. Really well
Planning is the most important thing to do if you don't want to end up with unfinished project, wasted money and nerves. There are lot's of wannabes posting a lot about camper van project but have never even started one, or stopped on the way with dismantled vans. To get the thing done you'll need step by step plan with calendar, contacts, tools, budget and timing. Plans that are not written on paper or in word document doesn't exist.
2. Save a lot of money
Car projects always cost more that you ever thought. In most cases people stop working on their project because they don't have enough money. Even in case of good plan you can never calculate all expenses waiting for you. So, get you life together and save lot of money first.
4. Buy a vehicle
This is the stage when you shouldn't make a mistake. Camper van is not a thing that you buy and sell every year. This is a dream project that will be with you for tens of years, so try to get as fresh vehicle as you can. Old ones will break you heart. In your country and region you'll have more options to check visually and drive by yourself. If you need a vehicle that can't be found in your neighbourhood importing is the only option. Once the vehicle is in your yard it will need to do some fixing. Try to do them before you'll start converting. Later you won't have time for it.
Your sleeping and cooking position is pretty much based on layout of camper van. Let's sort everything by priorities.
You can use wood and metal for furniture. Wood is easier to install, though will be spoiled because of driving vibration. So, I suggest to built metal rack for furniture. It's better to be done by the professional too.
10. P.I.M.P. it
Once you have a camper van its time for making it special. You can paint it in different ways, install spacers and A/T tires, stairs to the back or on the side of van, winch for off-road ones and etc. In this field the sky is the limit.
To sum up all you need is a good plan, a lot of money, inspiration and a good nerves. If you can't or don't want to own one - rent it here.