Hi Sundi, these are all really good questions - not all of which apply to my own practice, but I'll answer the ones that do
I *only* work on an hourly basis and don't offer retainers or discounts based on number of hours used - I want to simplify my billing system as much as possible and straight hourly allows me to do that.
I invoice every other Friday on net 14 terms with pretty stringent late payment policies for unpaid at 15 and again at 30. Post 30 are handled on a case by case basis.
While I think it's a nice gesture to offer a discount for payment on time it also kind of opens the door for late payments, which is something I have little tolerance for, as a small business. I think making the assumption that your clients will pay you on time (with failsafes like late penalties in place) helps set the stage for timely payments right from the start.
It's great that you're ironing this all out this week - it's a big step!