Hi,
A full discussion on icing would take an incredibly long time to type, but here are some pointers:
Clouds are clouds are clouds. For the most part you can't tell which ones will have icing in them and which ones won't, and then again some clouds will have ice in parts of them but not in other parts.
As far as TYPE of clouds go, you'll obviously find the most severe icing in thunderstorms, but you already knew that. The second most type of cloud you're likely to find some serious icing issues in are cumulus clouds. All cumulus type clouds tend to have larger supercooled water droplets in them. this means a high rate of accumulation and also generally means clear icing, both very hazardous to light aircraft.
Stratus type clouds are much harder to predict. The NWS does have a experimental product out which tries to predict where icing is *likely* to occur. I have not used it much so I don't know how accurate it is.
As far as practical advice goes, I make my decision largely on the type of aircraft I am flying and what the big weather picture is. As far as flying a single-engine aircraft with no anti-ice protection on it other than pito heat, I stay out of clouds above the freezing level, period. For multi-engine aircraft that have little or no anti-ice equipment it is much the same, although I might be a little (although not much) bolder because I have some excess power available to climb should I get some ice on the airframe.
The key to flying in icing conditions with just about every GA aircraft is "HAVE A PLAN ON HOW YOU WILL GET OUT" This is true even when flying aircraft certified for flight into "known" (whatever that means) icing. Unless associated with convectice activity, icing generally does not extend much beyond 4000ft bands. Climbing is usually the best idea to start with. As SOON as you start getting icing conditions, ask for a climb. That will give you the best opportunity to get out of it before you load up and cannot climb. The second option is to descend, but of course, not below your MEA. This is were you preflight planning comes in. Flying in widespread IFR conditions, with clouds and vis on the ground close to minmums in potential icing conditions in an aircraft that is not equipped to handle it is asking for trouble. You leave yourself very few options for getting out. So, as I said, ALWAYS have a way out. And that leaves me with the third option, which is to turn around and go back the way you came.
The next comment relates to your exerience. You obviously have no experience in icing conditions. I don't recommend flying to find icing conditions, but I do recommend that if you do go flying and you think you may enter icing conditions, take someone along who has experience with them. They *can* be very scary experiences, especially if you're not used to them. If you're headed to the professional pilot world, then don't avoid them altogether because one day you're going to have to deal with them. There are so many variables when trying to make a judgment call on the weather. Each circumstance is unique, and it takes many hours of making decisions about lots of different weather situations to really gain an understanding about how the whole weather thing really works.
Experience with weather is something that is not logged, but is crucial experience to gain on your road to become an experienced pilot who can make good judgment calls when the weather starts going downhill. One of the reasons insurance companies, airlines and other air carrier outfits like lots of frequent cross country time in your logbook is because it's the only way to gauge whether you have had to deal with some weather experiences. Quantity of flight time is easy to judge, quality is much harder.
I hope this gives you a small insight into the world of icing. If you have any further questions, I'd be more than glad to try and answer them. Like I said, a full discussion on icing is a very involved activity
Ray