It takes just one bad client to make you think about this... So true!
I'm hoping you are far enough in your career that you have other clients and other projects to work on as well. If not, read the next part; if you do, great!
If you have other work to do, then you need to explain to your clients what takes priority, what the due dates are, and that work does not continue without payment / escrow. As a freelancer, your time is valuable, and usually the only way you are making money. So, treat anyone who does not respect your time / life as someone who does not respect YOU / YOUR COMPANY.
If you have a large project you are working on for this client, it needs to have milestones setup that are definable, and have a clear indication of what is considered "complete" for that step. It will be included with the Scope of Work. The client should sign off on various stages, and money should be paid once work has been shown to have been completed, before additional work happens.
As for billing, make sure your bills go out on time and to the right address / recipient. Once the bill is sent in the mail or email, I set a reminder on my calendar for 30 days. If I have not received payment for that invoice by the 30 days, I send a reminder invoice, and a statement explaining that late fees apply unless the money is in my account in 14 days. If it's for a project, work would have already stopped while I wait, and the statement would reflect this. After that 14 days, a new invoice is made, including a late fee, and sent to the client explaining that they are past due. No work has been done otherwise with this client for the past 14 days, so not much is lost.
If the meetings are not being productive, then require them to send a meeting agenda ahead of time to all expected participants. If there is no use in you being there, explain politely that you have other projects to work on during that time, or that you are only available for xx minutes at yy:zz time. Set the limit, and stick to it! We've all wasted lots of time in meetings that could have been better spent elsewhere. You're the expect on your time and craft, so make it known!
If you do not have other clients, you can still use a lot of the advice above - remember, you need to spend time working on yourself / your business, and that also includes finding NEW clients as well. If you are stuck having just one client, then you are essentially an employee without benefits. Explain that you are busy during the meetings that you could do without, and use the time to expand your business, in any way you can.