karen's answer, although does not cover all cases (like her answer fails to address how should $300.23 be written), her answer was still able to answer the question correct.
By the way, the correct way to write $300 is Three Hundred and 00/100. 00/100 indicates no cent.
用英文填寫支票方法如下:
1) (Sender's name and address); printed otherwise to fill in the space on the upper lefthand corner of the cheque;
2) (Numer of the cheque): printed on the upper righthand corner of the cheque;
3) Date:as shown below (2) and to fill in so as to indicate when payment will be made or debit one's account.
4) Pay to the order of: to fill in the recipient's name in the middle part of the cheque and then the amount of money to be paid on the same line as HK$300 and then on the line below "Three hundred dollars only";
5)( Memo) : to fill in the space of information for future reference which is located in the lower lefthand corner of the cheque;
6)(Signature): to fill in the space with official signature as recognized by your bank and which is located on the lower righthand corner of the cheque;
用中文填寫支票方法如下:
由1)至3) 和5)至6) 填寫的方法同英文支票差不多一樣;但是4) 的收款人姓名可以用中文填寫,而有關款項;上一行用中文港幣$300元 及下一行"港幣三佰元正";