I combine shipping whenever possible to the same address/eBay account unless otherwise requested.

Slower method, but you see shipping cost prior to paying: order all of your items, DO NOT PAY, get combined invoice from me, pay, then I ship.

Fastest method-order all of your items, pay, I adjust your invoice for any over-payment and ship immediately.

As a general rule (90+% of the time) , more items = significantly lower shipping costs per item.