If you are not one of the unlucky ones to have their email account compromised and large numbers of emails sent on behalf of you to your entire address book don't wait until it is too late. Get into your account and change your email password as soon as possible.
If you receive an email from someone you know and it looks a bit weird, for example, just a link in it DO NOT BE HASTY and click the link. If you are not expecting anything from the person check with them first. Your best defense is to use a simple phrase.
"If you're not sure - delete it"!
If it is really that important I'm sure you can get the person to send it to you again which generally costs less to do compared to having to restore your computer to remove a virus.
Randomness - plain and simple! In most cases you will use a program like Outlook, Windows Live Mail, Thunderbird etc to download and view your email on your computer therefore setting a strong password of random numbers, letters and other special characters such as + ? & etc generally means you only need to enter it once and tick the "Save Password" option and away you go. If you access your email via a website then maybe typing in the password over and over again might be a little bit more tedious.
The main question you need to ask yourself is this. What does it mean to me if someone gets into my email account, sends emails with a link to download a virus?
If you don't care then the chances are that you can go on using the same password as you are now but next time you get an inbox full of spam don't complain ... weak passwords inevitably lead to account compromises and access for spammers to send their inbox filling junk to the rest of us....
If you are a business and you are using one of the free email providers and you hear yourself saying, this is not good enough, I rely on the email for my business... You should take a long hard look at the services you are using for your business email. You should look at having a dedicated domain name and hosting for your email which can cost as little as NZ$300 + GST per year for a light email user.