Manga (Japanese comic) is always right to left (and then top down). If there is case of it being otherwise, chances are that the author will mention it. Manhwa (Korean comic) is always left to right (but read top down first if they layer the panels oddly). You can tell the two apart from the drawing styles (particularly panel placement) and names (Akihito vs. Chul-su). Manhwa is also more likely to have all the chapters in full color; manga might do a few color pages in the beginning of a chapter but it's very rare for the whole thing to be in color.
Manhua (Chinese comic) I haven't really run into on Mangago, but the few I have read were pretty much the same as manga but with names being Chinese (ex. Chenguang) and also having the entire plot set in China. It looks like they usually have more characteristics though so I'd suggest doing more searching with those if you're interested.
Hope that helps. I remember it took me a bit to get the hang of what was what reorienting how I was reading for each. Totally worth getting used to the different reading styles though; manhwa has gotten ridiculously good in the yaoi realm over the last couple years.
is it from right to left or left to right o.e. first time im confused of the way reading it LOL