There are different ways to decline an offer, depending on the history of your contact with the employer or recruiter. If the offer comes in an email or a voice mail message, your best option would be to promptly respond in the same format. A more formal way to decline an offer is in writing. Declining an offer is not always an easy task. Regardless of the media form used, It is important that you display your professionalism throughout all stages of the job search, even if you are not interested in the job. It is to your advantage that you communicate your decline in a professional matter, as a courtesy to the organization and as a good business etiquette. The basic components of a rejection/decline letter include the following.
Paragraph 1 (Opening paragraph) — Greet the employer, and thank him/her for the offer.
Paragraph 2 (Your Decline) — Communicate to the employer your decline of the job offer and reasons for declining the job offer. Be tactful and reasonable. Simply stating something like: "it's too far to drive." may sound immature or self-centered. However, if you explain that the current cost of gas combined with the part time hours offered are just do not make it economically sound for you to accept, the impression you leave will be more positive. And who knows, maybe they will call you back and offer you more hours?!
Paragraph 3 (Closing Paragraph) — Provide a positive closing, wishing the employer luck in his/her search for a candidate. If appropriate, offer to assist the employer with a referral of someone else you know that might be a good fit for the job.