Most people do not decide in the first conversation. They want to think, talk to someone at home or compare. Many sales are lost after a good first talk, simply because nobody got back in touch.
Agree on the next contact
Before you part, agree when and how you will be in touch again: a call on Thursday, a message next week. Then the follow up is expected and does not feel like pressure.
Keep it short and friendly
A follow up message needs only a few lines: a reminder of what you talked about, an answer to any open question, and the agreed next step. No long sales text.
Bring something useful
If you can, add something of value: the answer they asked for, a short explanation, the date of an event. It gives the message a reason.
Know when to stop
If someone says no, thank them and leave the door open. If they do not answer after two or three tries, stop for now. A respectful ending keeps your name in good memory.
Keep notes
After each conversation, write down what was said and when you agreed to follow up. A simple notebook or a list on your phone is enough. Without notes, follow ups get forgotten.