You can purchase your tickets early online, but the ticket website is in Japanese. You can either use google chrome or translate on your phone to read through the menus. You can also purchase tickets at any Japanese 7-Eleven using their copy/ticket machines (about Y500 more expensive, but worth it). A little work to save you a lot of waiting time in line. Also, check the night prior what the weather would be like so you don't go any days when you can't see anything.
If you are a foreign tourist, and you really want to make it up to the top while there is a long queue, it may be worth it for you to buy a fast ticket for 4,000Y. It covers both observatories, and from getting in line to buy our tickets to getting up there had to have been about 5 minutes total! (We were told the queue was at least an hour at this point.)
There are also goodies you can only buy in the shop at the top of the Skytree, so you can pick up an extra special souvenir to show you made it up there.
Great view from above for a lot of money, however it is pretty difficult to find the right weather. Days with clear sky are best, but not always give you a view to far away Mt. Fuji. Before going up check the newest photos on instagram to get a hint how much you can see that day.
Tokyo skytree has great views of the city below. It can get quite busy at times but if you go earlier in the morning or a bit later at night there is less of a chance you'll get stuck in a super long line :)
If you plan to go, try to schedule your trip here on a day when the weather is clear. The view is great no matter what, but a clear day will increase the view by a ton
The best tower in Tokyo, MUCH bigger than Tokyo Tower which is very small. Solamachi is the mall under skytree and its pretty great. There are lots of great gifts to buy people if you are a tourist. The food court is really nice too!
Tip for foreigners. There's a separate line if you hold a foreign passport. I'm not sure if the prices are different for foreigners, but we didn't have to lineup. We received our tickets pretty quickly by visiting a small counter behind the huge lines.
Nice views of Tokyo! Get the best of both worlds by going around dusk.
Usually, it's super crowded— long lines, and sometimes tickets even sell out.
It costs more, but you can skip the lines with a Sky Tree Fast Ticket which are only available to foreigners*, so make sure you have your passport!
*If your Japanese friends are with you, then they can purchase a Fast Ticket as well.
You can order advance tickets online, but the catch is that you need to be able to read Japanese and have a Japanese (issued) credit card.