How to eat a healthy vegan diet?

Less processed food. You may have an unhealthy vegan diet if you add too many processed foods. Granted , they may be better than non vegan choices. Using whole foods whenever possible is a good start.
Check these sites. They don't give us enough space here to fully answer to your question but here are links to some excellent websites that will give you great guidance & provide quality information on starting a healthy vegan diet: http://www.21daykickstart.Org/http://www.Vrg.Org/nutshell/vegan.Htm, http://www.Veganoutreach.Org/guide/index.Html, http://vegandietguy.Com/ and http://www.Happycow.Net/vegan_diet.Html.