It can be very confusing sometimes because so many come out that most Comic Shops don't come anywhere close to carrying them all. You can either buy comics at a Local Comic Shop (LCS) or from an on-line mail-order subscription service. One thing to keep in mind, whether you buy in person or mail-order, you definitely want to know what you want in advance.
There is a huge catalog that comes out every month (typically on the last Wednesday of the Month) that details the comics that will be coming out 2 months down the road. This is published by Diamond Comics Distributors and is called Previews.
The Previews catalog contains blurbs from all the publishers describing their upcoming offerings, usually with a cover image and short blurb talking about the issue. Sometimes there are also sample pages from the comic or even interviews with creators. It's a fascinating reading experience, it gives a great indication of just how much variety is out there. It can be bought at most comic shops.
Another thing to consider, if you're buying comics "off the rack" from your LCS, is if you don't let them know what you want, the comics you want may be sold out or might not even have been ordered by the shop at all. If you want to get various comic series regularly ask your LCS if you can start a "Pull List". That way they'll put aside what you want and it will be waiting for you when you go to the shop.
Aside from the Previews catalog, there are other ways to know what's going to be coming out. Many of the publishers also put out press releases about their upcoming solicitations starting about 2 weeks before the Previews catalog is published. The same information that goes into assembling Previews is posted up on many of the major comics news sites well before the catalog hits the street. This means you can see what's coming out from the comfort of your computer screen, no need for a catalog. The only problem is that these are generally scattered all over the place and hard to find in one spot. Doing an internet search for the publisher name, month, and year can help find these like so:
Search: "Image Comics" +December +2016 +solicits
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