Small Scale Military Headquarters

Hi. I'm not new to the board, but I have some things I want to sell and this is the first time, and I have a few questions. First, who do you guys use for shipping? I've had good expirience with UPS and USPS for buying things, although UPS has a much better tracking system.
Second, how do you guys figure the shipping on an item before it's sent? I was just going to take it to a UPS or USPS shipping center, but how would you know how much to charge the buyer for shipping if it hasn't been shipped?
Thanks for any help!

C-7A Caribou,
If you look within the Buy/Sell/Trade section at other peoples posts, you can get a feel as to how it is done.

Here is what I do:
Usually I will post an item with a price (plus shipping).
Once you have a person who has committed to buying the item, ask them for their zip code. Once you have a weight (I have a postage scale at home) and their zip code you can figure out the shipping cost.
I use USPS because we have a local Post Office that is open 24 hours/7 days a week. I assume you can go online with UPS and figure out shipping cost before shipping out the item.
Once you have your shipping cost, email back the buyer and let them have a total cost (price + shipping).
I do a delivery confirmation on all the packages I send out. This enables you to have a tracking number if a dispute where to happen that the buyer said he/she did not receive the package.

You might want to read the sticky post on trading in B/S/T area before you post an item.
You can pm me if you have more detailed questions.

For trades, I let the buyer know that shipping will be my actual cost. Most everyone here has shipped similar items themselves so they know roughly what it will be. Then I ship via USPS and then let the buyer know what the actual cost was. I have the receipt ready just in case there are questions, but so far this has worked really well, even for overseas shipments.

I only deal with people that I know from the board so I think that has helped avoid some of the bad situations that occur.

As for ebay, I pack the item as I would normally send it. Then I weigh it with a normal home scale which is close enough for me and put that information into the USPS website to get a shipping estimate.

If you have not buy/sell/trade before, a board member may ask you to send your end of the trade first before they send their end. Don't be hurt by this. We have had some characters swindle board members in the past and we tend to be a little gun shy with new people. Once you have a made a few trades and people know they can trust you, this process would not be necessary. It just depends on the individual.

Thank you guys for all the help. I'm selling a 1:18 109, and it will come in handy.