1) Do not go for the weather. It can be beautiful blue sky or misty, rainy, or snowy. Come prepared for all possibilities and enjoy the forces of nature.
2) Mid-June through mid-August are by far the busiest tourist seasons. So, if you want to avoid the crowds, go in May, early June, late August or September.
3) Iceland lies just below the Arctic circle. Therefore, the sun does not set until midnight in the summer, and winter days can get as little as 4 hours of sunlight a day.
4) Puffin season is from early April until September. Whale watching follows the same.
5) Ice cave tours and Jökulsárlon boat tours operate generally from April through October.
6) PLEASE respect nature! Stay on trails and do not create your own. Pack it in, pack it out when hiking. Do not leave trash or tissue paper anywhere. And be careful with those selfies. Guiderails are often non-existent.
7) Public transport is spotty in Iceland. No trains, and buses are infrequent. If you will not be taking day tours or multi-day tours with a company, you will have to rent a car. Most roads are accessible with a 2-wheel drive but several, especially in the highlands and in winter, require a 4-wheel drive.
8) Although Icelanders are incredibly proud of their unique history and language, English is widely spoken as well.
9) I would not recommend traveling the entire Ring Road unless you have a minimum of 12 days in Iceland. You could do it in 10 days but will be in the car quite a bit and while the scenery is gorgeous and otherworldly, you will miss many opportunities such as whale-watching, hiking, snowmobiling, glacier climbs, museums, etc!
10) Take a horseback ride at some point, but do not call the Icelandic Horse a pony! Yes, they are small but full-grown.
For more advice on Iceland travel, what to expect, and must-see places, catch my Travel Tales with Mike Siegel now.