Passport validity:Foreigners wishing to enter Turkey should carry a travel document (passport) with an expiration date at least 60 days beyond the “duration of stay” of their visa, e-Visa, visa exemption, or residence permit.
Further information and exceptions you can find here: http://www.mfa.gov.tr/general-information-about-turkish-visas.en.mfa
Passport/ID validity is very important, we have already seen people denied to enter the country due to expired passports!
Visa legislation:The best and most up to date information you'll find at the website of The Ministry Of Foreign Affairs of Turkey:
Countries whose citizens are allowed to enter Turkey with their national ID’s for a stay of 90 days:1. Germany
5. The Netherlands
9. Turkish Republic of Northern Cyprus
Online Visa:All citizens of other counties can apply for online visa here: https://www.evisa.gov.tr/en/
A national driving license is enough!
A driving license for motorbikes is necessary for renting a bike.
Health insurance card:Must be valid for foreign countries! Ask for the Asian part of Turkey also.
If possible, private hospitals should also (or especially) be covered