Trusting others in a relationship actually begins with trusting yourself. Our lives are the result of decisions and choices we have made. Each of us (chooses our own) friends, lovers, and spouse. When things go wrong the natural tendency is to blame the other person. However if you go to the grocery store to purchase an apple but buy an onion instead...Whose fault is that? No matter what happens in our relationships we cannot escape the fact that we (chose) this person and said (yes) to being with them at some point in time. That's very empowering!
The reason it's empowering is because we have the ability to learn from our mistakes and make better choices for ourselves in the future. One thing I would suggest is actually taking the time to do some serious introspective thinking about what you want in a mate and write them down. The next step is to have the self-discipline to stick to your own "shopping list". Keep in mind one very important purpose of dating is performing "due diligence". Aside from enjoying going out you are suppose to learn if this person (truly) wants what you do as well as observe their actions.
It's been said that women fall in love with their ears and men fall in love with their eyes. However with age comes wisdom. Men learn all that glitters is not gold and women learn that actions speak louder than words. Best of luck!