If it is a regularly occurring account, such as Truck washing etc. I would not send a thank you card. One time shot deals such as Decks, etc. I would send them one witha small discount coupon. Preferably one that can be used after you give them a quote. This way they might be willing to pass it on to any friends, neighbors, or business associates.
Bid Sheets;
I do not use them because of my type of business, Truck washing, but I do use a quote system. The first thing is that I NEVER give out a quote over the phone. I always make the effort to go see and meet them. There are two reasons. The first is I don't like to give competition a leg up by being able to call for price comparisons. The second is that I am so charming that people can't refuse me once they meet me. (strike that) The second is that is a lot easier for someone to say yes to a real face then to a voice. It is part of the building of the relationship of trust.
Invoicing: I use quick books pro. It is relatively inexpensive, it tracks the finances really well, and the invoices are very customizable. That means that you can put in any field headings you want on the invoice and it will print it out. You can also put a memo on the invoice that the customer can see and one the customer can't see. Sometimes you might want to remember that the customer is a real jerk, so that their price needs to go up with the hassle factor. One thing about Quickboks is that you might want to have your accountant help you set it up, and if you don't have an accountant, in my opinion you are a fool. A good one can make you a lot more than you will save in not having one. The nicer and more professional everything looks the better you will look.
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If Vegetarians eat vegetables, what do humanitarians eat??
Just a guy driving around trying to make a living washing trucks, Wouldn't know a deck if it bit me in the hind quarters,