I'm still new at this, especially at the estimating part, but one time I think I did it perfectly. I was asked to bid a BIG job (for me) - four removals, 24" dbh and 30" red maples, 36" black walnut, and 64" silver maple. Only a few branches were over a shop. Silver maple roots were lifting and cracking the concrete floor of the shop. Anyway, I was trying a new method of walking around, estimating hours for each tree, putting the numbers together, and I gave the homeowners a price before I left the property. $4500. They looked a little surprised and asked if that was really my price. A few days later I called to find out if they made a decision. They said a large tree company, before I came, had given them the price of $4400. I felt highly affirmed that day. Good bid! (And the job was probably too big for me anyway, would have had to rent a skidsteer.)