The safety of your data mainly depends on the strength of your key. Please refrain from using the name of your dog, cat or favorite movie and do not use any password you ever used as your key. This includes the password you chose at signup for PwdSafe. As a rule of thumb, the longer the key is and the more different characters it contains, (numbers, uppercase, lowercase, special characters) the safer it is.
We suggest to either use a long but easy to remember sentence like for instance 19GreenUnicornsEat42VegetariansIn10Minutes or a (shorter) password with at least 10 characters which includes, uppercase, lowercase and special characters as well as numbers. For instance: k$HdpSd)1#P. Each time you want access your data you must enter your key. So to use a too long key might be cumbersome and to choose a cryptic key might be to hard to remember. It's up to you and your preferences - at least this is the only password you will ever have to remember. Please do not use these examples.
If you decided on your key, write it down on paper and put it somewhere safe, maybe the ring binder where you keep your important documents. Then memorize the key. And please, please do not store the key on your computer.