Reuse of passwords
Like many people I have a number of accounts - but many of them are for sites like the register where the consequences of a hack are insignificent. For such sites I often reuse simple passwords - for other sites with financial data (eg PayPal) I use strong passwords that are unique to each site.
An easy way to generate fairly strong memorable passwords - concatenate a car registration number, a friends name and the name on a bit of equipment.
eq XNO123SWendyHUDL2 (not a password that I have ever used!!!)