This may go without saying, but the more timely you are as a freelancer, the more success you will have. Remember that your goal is to delight your clients and solve their problems. The less they have to wait, the better.
If you can't be on-time to a meeting, whether in person or online, you aren't being timely.
If you can't respond to a request from a potential client within 24 hours, you aren't being timely.
If you can't send the client an estimate within 24 hours, you aren't being timely.
If you fail to meet the client's deadline, you aren't being timely.
Get the point? Being timely isn't optional as a freelancer. Timeliness is essential to success. Get your act together, set up whatever systems you need to guarantee it, and commit to it.