I've taken online classes for over a year now. I've also written essays and reports comparing online schooling to traditional in person schooling. As someone who's looked it up for research and done it for a long time now, it's like this. Anything that you know how to do like English, Math, etc or advanced classes in any subject that you are good at and have never had a problem with, take it online. It's usually very easy and you can work at your own pace. If something is completely new to you I strongly suggest you take it in school. Theres nothing worse than waiting for a teachers response online when you have a question. Very irritating.
Anyway, the basic way it's gonna work is, every week you'll have assignments, submit them at the end of the week, and you'll have to post in a forum discussion, along with other members of the online class.Your assignment difficulty and reading will vary, but as for forum discussion, all of mine have required at least 3 posts a week, and the posts have to be related to the forum topic and contribute in some way of intelligence. The best way to go about this is to make sure, everyweek, that you are one of the first people to post in each topic( I normally have about 3 topics a week that each require 3 posts a week). Also in the middle of the week and nearing the end, get in your post quick before things get crazy. You don't want to have to read a ton of other people's crap in order to avoid repeating them.
The difficulty of online classes is compeletly determined by you. Just use your judgment of what you might need on site help with and what you wont and plan accordingly. If you need to know more I can probably help. I've done online courses for 3 schools and they were all very similar in structure