If you have a set of tasks that you wish to follow either before a sale or after - the system allows you to create automated campaigns these aren't only for emails but also other areas of the system such as tasks and leads/sales.
To do this, you will need to go in to the Email section > Click on Automated Campaigns and Create a new Campaign. Here you will be able to create that sequence of tasks and start the campaign.
Once the campaign has been started - simply add your contacts by clicking "Manage Contacts" and searching for the relevant ones.
These tasks will not send you reminders but will appear in "My Day/My Week" (on your home page). Once the campaign has started and you wish you add further steps, unfortunately you aren't able to.