Where possible, have your notice ready in writing to hand deliver.
Include, that after careful consideration you have decided to leave the company. Clearly state the number of weeks’ notice you will work and your last date with the company.
Be professional with your reasons for leaving.
Focus on the new job and what it can offer you. If there is anything negative to say then save that for your exit interview.
Discuss it with your recruiter.
Having spent time getting to know you, your consultant can provide additional advice on how to tackle this head on.
Don’t burn any bridges.
Thank your boss and focus on the positives of the job. If you must tackle anything negative then be constructive.