I use a day planner to keep track of all of my appointments, work schedule and as a day log to record what I actually do. I keep it in a zippered leather cover that has room for my calculator, business cards, pens/pencils and a spot for a note pad. I also keep a printout of my current customer contact list from Quickbooks in it. Here's the day planner I prefer....just got my new one in the mail yesterday in fact.
I also have an aluminum storage clipboard that I keep in my truck which has some marketing materials in it, blank lawn maintenanace agreements, 3 part estimate and invoice forms and a note pad. I tend to use that when I'm doing estimates for new customers or for installation and renovation estimates as well as for field invoices. I just use generic forms I get at Staples for that. My aluminum clipboard is similar to this, but it opens like a book instead. http://www.amazon.com/gp/product/B00...&creative=9325
P.S. - The day planner also has sections in it for notes, to do lists and some resource information in it like important dates, international holidays and area codes. I keep track of my non-mowing to-do list and have my mowing and plowing lists in those sections.