In the long run, we need support from our friends and supporters to get along in our work and our lives. Have you ever gotten assistance from someone who did all the wrong things and made matters worse? That's what it's like to get a poorly thought-out recommendation.
Good recommendations are specific and useful. It doesn't actually take much time to write them, usually, but it takes time to think the situation through and make a real contribution. After you've figured out what to say, don't take too long to get it out. Awkward sounds genuine.
The Public Speaker: How to Write Better Linked Recommendations, 2012-Nov-13, by Lisa B. Marshall
Try to keep your recommendations 60-100 words. If possible, follow the rule of threes. When you group together in groups of threes, it makes it inherently more effective, more satisfying. Oh, and try to choose adjectives that are specific, interesting and somewhat unusual such as pioneering, illuminating, vibrant, vivacious, amazing—you get the idea.