How Do I Add or Remove a Lead from a Followup Campaign?

On the Lead Detail page, to the right under Lead Actions, you can add or remove the lead under the Campaigns heading.

If you want to add the lead to a campaign, just click in the area under Campaigns and click to choose the Campaign you want to add them to.

If you want to remove the lead from a campaign, just click on the x on the Campaign tag. This will delete the Campaign tag, thus removing them from that Campaign.