Start by choosing a restaurant that is affordable for everyone. Then, if each person's expenses end up being fairly even, you can split the bill equally and agree to a tip amount.
But, as we all know, the tricky part is when people order items with vastly different costs. Or, when one item — like a bottle of wine or an appetizer — is shared by only some. Regardless of the situation, as a general rule of thumb, expect to pay for what you ordered and enjoyed.
To ensure clarity among the group, if you want to order an item to share, throw out the idea before ordering and see who else is interested — and then those individuals should be responsible for covering the costs.
If you find yourself in a situation where you are being asked to pay an amount way above what you actually ordered, there is no harm (or shame) in suggesting that the bill be split more or less according to each person's order. Finally, when paying for your portion of the bill, come prepared to use cash. The last thing you want to do is wrack up credit card debt by dining out.