Writing a Strong Recommendation Letter for Medical Residency

Hello everyone! I'm currently in the process of writing recommendation letters for medical residency applications, and I have a few questions. First, what is the ideal length for a recommendation letter? Should it be one page, or can it be longer? Also, how should I format the letter to make it look professional? Are there any templates you recommend? Lastly, what should I focus on when describing the applicant? Should I mention specific examples of their abilities, and how important is it to tailor the letter for each residency program if they're applying to multiple ones? Thanks for your help!