A very simple and quite secure way is using a nonsense sentence:
So you think of a quite absurd sentence like:
My 20 horses go fishing every second weekend and Maggie Thatcher watches them every time.Especially on the 17th of march!
This gives a atrong password:
And a very strong if you ad some special signs:
Of course the password has not to be that long, about 12 signs should be enough, but the longer, the better!
So, the password above could be for high security tasks, like disk encryption and the one beyond a password for a not that important forum,…:
My 20 horses go fishing every second weekend.
Another possible method is Diceware, which gives you a certain number of random words as password. The method is well explained on the linked page, so all I want to give here is a small tip:
if you have your diceware password increase its security by adding some special characters and numbers, one number and one character will be easy to remember, but increase the passwords security a lot:
dogcarhouse*flower1gamechildren is much harder to crack than
dogcarhouseflowergamechildren, due to offering more possibilities…, but I prefer method number 1!