Whats this about?
Living vegan, e.g. only eating plant based food, is a good thing for various reasons. No animals have to be held in farms or have to be slaugthered, and the production of plant based food consumes less water, fertilizer, space, and causes less climate changing gases. However, there are some best practices one should have in mind when living vegan, as staying healthy is more difficult than with other forms of nutrition (the easiest to do is pesco-vegetarism, e.g. eating fish and plant based food only).
Essential supplements
Vitamin B12
Vitamin B12 is a essential vitamin that you can't get out of plant based food, and that is important for your neural system. You'll need to get it elsewhere. Some manufactured food and toothpastes contain B12, but usually not enough to ensure you stay healthy - for this you'll likely require either pills or drops. Usually, a vegan living person will require 50-250µg per day.
It is strongly recommended to make a check-up on your B12-Level once per year in the first few years of living vegan; if you've been stable for some time, you can reduce this to every second year.
Ask your doctor to test your "Holo-TC"-Level (should be between 40- and 100 pmol/l), as other markers are unprecise.
Vitamin B12 is essential, and not taking it will harm you in the long run. If you aren't willing to take it or check it, you better go on eating camenbert. Note that too much B12 is also dangerous, as it might increase the risk of cancer.
Calcium
Many vegans seem to suffer from weak bones; to counter this, get either calcium-containing water (the more calcium, the merrier), or consider taking calcium pills as well.
Omega3-Fatty-Acids
Another one that you won't get easily, and needed for your cardial system. The best choice you have is linen-oil. Pour it over your food, but never heat/cook it as this would cause it to break into toxic substances.
Cooking and nutrition
Much fresh vegetables
As a vegan, you should try to eat fresh vegetables daily. Your main meal should usually contain at least 3 different kinds of vegetable, one of them green. Spinach and mache are valueable sources for iron, mushrooms deliver vitamin D.
Fruits
Try to eat fruits daily, shun other sweets, dried fruits and sugar (this is especially true for acorn-syrup and other fructose based sweeteners). Getting an problems from sugar of fresh fruits is next to impossible (if you have no prior history of Diabetes), even if you consume up to 100g of fruit-sugar through fresh fruits; the only thing you should be a bit careful with are grapes.
Proteins
You need to get proteins for your muscles. Soy products are important if you want to live vegan, as they containt rare protein elements; try to incorporate tofu into your main dishes; lentils, pees, and peanuts are also good sources for proteins.
Nuts and seeds
Nuts and seeds will offer you additional proteins, minerals, and fats - try to incorporate them into your daily nutrition. Especially Almonds, Walnuts, and Sunflower Seeds are important. Be careful with Brazil nuts, Chias and Linen-Seeds (rather get the pressed oil of the latter one) as these contain toxic substances.
Use wholewheat
Using wholeweat will furhter help you to get iron and minerals. It might take you a bit to get used to it; if you have problems, try to increase the amount slowly.
Evade highly-processed food
Highly processed food contains much salt, fat, and few things that help you to stay healthy, so its best to evade those. The amount of sugar you consume per day, be it through sweets or your normal food, shouldn't be on 25g per day on average (less is better, you don't need any sugar to live). If you don't live in a desert, use as less salt as possible.
Eat enough, don't fall into underweight
As a vegan, you are much more likely to suffer from underweight than getting overweight - so try to hold your body-mass-index at 20 or above. If you have trouble, bananas and (sugar free) peanut butter are good ways to gather calories.
Drink enough water
1.5 litres should be your minimal consumption; it helps to stay fit and reduces the risk of various health problems. More is better.
Behavior
Evade drugs, and especially smoking/vaping
Drugs are a great risk when it comes to health aspects, and even more so for vegan living people, as there are overlaps between the risks from drugs and the side effects that might occur if you mess something up with your nutrition - you don't want this. But basically, this is for everyone: Don't fall to use them regulary, or they'll bite you. This is especially true for nicotine, as its risks might be increased through the consumtion of vitamin B12 (which you absolutely need as a vegan).
Sport and training
This is true for anybody, regardless of the nutrition: Doing some sport will greatly increase not only your life-expectation but also the quality of your time. No need to go for high results, just try to go jogging on a regular basis and do simple, weightless gymnastics. Most people in modern societies sit far to long per day, and thus develop chronical pains.
Conclusion
This might seem like a lot, but doing these (or at least trying to do so) will greatly increase your chances of living a long, healthy live as a vegan. Have fun!
PS: Vegan-adapted version of the germans food agencies 10 rules for healthy living.. Also worth to keep in mind if you are (still) a vegetarian or carnivorous living pal!