There are many websites that can assist with vegan meal planning while out, but be prepared to have quite a limited selection. You will also need to speak to your wait staff to specify you need a vegan meal - not the easiest thing to do if there is a language barrier.
Some chains do offer a vegan selection, but it wont always be possible to force your none vegan friends to eat where you need to.
Last night I went to Wagamamas, a past favourite restaurant of mine that we haven't been able to enjoy since Chris's misdiagnosis of being coeliac. It was rather impromptu I didn't check their website and when I found the menu lacking marked vegan foods, I chickened out :(
Trying to at least stick to vegetarianism, I selected a Yasai Katsu curry - It was delicious, but sadly not guilt free :( - It contained both egg and cow milk doh!