1. create strongest password yourself, or here
2. apparently, it's better to use different password for each account, but how can one remember all those facebook, skype, gmail, metanorn passwords? use a password manager. my all-time favourite is LastPass.
3. check the strength of password here
4. always checked whether your email has been hacked here.
5. remove passwords in browser if you're going to sell or give the computer away
Firefox : Tools > Options > Security > untick 'remember password for sites' AND click 'saved passwords' and click 'remove all'
Chrome : Spanner icon > Options > Personal Stuff tab > select 'never save passwords' AND go to 'manage saved passwords' and remove the sites listed there
I hate Internet Explorer, so, nothing for it here.