Repost from here:

1-Webcomics are advertising not a product. They are about building and audience that trusts and likes you.
2-The more you cater to and undeserved community the stronger the trust/like of you there will be.
3-Copying a popular webcomics will not work because the audience already has a webcomic for them.
4-You can only make a webcomic about something you know. Posers will fail horribly even if the idea is good.
5-To succeed in building trust/like you must stay actively involved in online communities related to your comic.
6-Once you have built and audience that trusts/likes you (apr 5K reader) you can sell them things to make money.
7-It generally takes 3 years for a webcomic to see any type of financial success.
8- No one will buy anything from a site that has been around for less than half a year or has less than 30 comics. (unless you are famous)
9-You can only sell things that the audience would buy normally and the product must be quality.
10-People won’t buy things with your logo/characters on it. Sell things that people would buy without the comic.(unless you’re famous)
11-To build an audience you must bring people back to your site every day with new and engaging content.
12- Paysites, T-shirt, prints etc can all sell to a receptive audience provided you have free content to bring people back every day.
13-The harder you make it for people to view your site the smaller your audience will be and the less sales you can make.
14-Flash viewers, animation, sounds make it harder for people to view your comic thus lowering your audience.
15-Sex sells but sex with no substance of story and quality of art behind it will turn your readers off.
16-Most new viewers to your site only spend 45 second on your site. You must catch them in that time.
17-The art and web design must be clean, understandable, evocative and constant style to catch a reader in 45s.
18-Art does not have to be good. Just easy to understand and matching the comic theme to catch new readers.
19-Good writing will help keep reader, built trust/like and help market your comic virally. It will not catch new readers.
20- Paying for advertising works as long as you spread your money out over a long term instead of spending at once.
21-Participating in forums/twitter/facebook can be free advertising of your site provided you don’t look like your advertising.
22-To advertise without looking like advertising have intelligent conversations and your comic link in your signature.
23-Troll are to be ignored. Do not speak to them of or of them. Anything else will encourage their actions.
24-Put your comic up today. It will never be “good” in your eyes but it is “good enough” right now.
25-Your skill will improve through practice and dedication to putting a comic online.
26-Be open to criticism. Your readers will tell you what you are doing right and wrong.
27-But don’t be bullied by your readers when it comes to story. Technical flaws should be corrected the story is your own.
28-It is possible that you suck and you won’t have a career as a webcartoonist. You will never know till you try for 3 years.
29-Webcomic creators are lonely people. Send them questions on email. They will probably respond and help you.
30-Everything you need to know about making webcomics is online for free. You don’t need to pay for the knowledge.