1. I want to check out.
我要結賬。
還能這樣說：
I'm going to pay.
I want to settle the bill.
應用解析：
check out 還有別的意思：檢查；通過能力測試；試試，看看。
例如：Would you check out your change?
請檢查一下找的錢好嗎？
2. How can I pay?
我要如何付錢？
還能這樣說：
What way of payment can I choose?
How shall I give it to you?
應用解析：
pay up 付清全部欠款；
pay-as-you-earn 預扣所得稅法；
pay sth. out 花費；放松；
pay for sth. 為某事吃苦頭或受懲罰；
pay sth. back 還給某人
3. Can I buy it on installments?
我可以分期付款嗎？
還能這樣說：
May I pay by installments?
Can you sell it to me on an installment basis?
應用解析：
installment on sth. （分期付款的）一期付款。
例如：keep up the installments on the house 為買該房按時分期付款
4. Will that be cash or charge?
您是用現金付賬還是用信用卡？
還能這樣說：
Would you like to pay by cash or by credit card?
How are you going to pay, in cash or by credit card?