Don’t assume people will know what you want them to do when they see your ad. Be clear and straightforward with your desired action and explicitly say “follow us”, “click to read more”, or “reply with your favorite [insert here]”. This practice is especially important for follower and engagement campaigns, but is a best practice for all campaign objectives.
If you’re not sure what your desired action is, focus on that before starting your campaign. Consider what you want your target audience to feel, think, and do when they see your ad — and go from there.