If you’re travelling by train, try to do your travelling during the day. Bern’s train station can be dangerous at night when lots of drunk people congregate. Drunk people can pose a threat depending on the situation, so it’s best to avoid.
Always carry some form of identification on you. Police officers will sometimes do random checks on tourists, so having a document to prove you are who you say you are is always handy.
Even when you’re travelling in unfamiliar areas, always look confident and like you know where you are going (even if you don’t!) Thieves will be on the look out for people that might show any signs of weakness, so don’t give them an opportunity.