We have outlined what to include in the terms of service. The things not to include there might need a sum-up as well. Why? Because it will cost you money. Lots of money. Mucho dinero.
In most European jurisdictions there are severe consequences for including and benefiting from abusive clauses in contracts, terms of service and privacy policies. These generally fall under one of the three categories:
So what to avoid?
Well, the milestone for customer protection in Europe was the DIRECTIVE 93/13/EEC of the European Commission. It's been amended at various points, though.
There are, however, useful and more precise listings of local authorities, among which there are the guidelines for:
In some cases, such as in Germany, you can make an appointment and consult particular clauses with the local branch of the customer rights organizations. Keep your eyes open for workshops and lectures as well. Don't assume the print is small enough.