In regards to cichlids and planted tanks, you will need to be very selective with your stocking choices. Angelfish are a no brainer, as are Rams and Kribs. Discus do well in planted aquaria, but they are notoriously difficult to keep.
Outside of these, you have to be very careful.
The first thing to consider is the relationship between your tank size and the adult fish size. In a 30 gallon, you are limited to the dwarfs and the smaller Central American cichlids such as the Thorichthys species, most commonly the Firemouth. At full grown adult size, 2 would most likely be the limit.
Second thing to consider is the temperment, both to each other and their tankmates. Even angelfish can display a mean streak, although it rarely results in death (save for neons or other small tetras which become dinner). The smaller Central American cichlids can be downright nasty, but it depends on the individual. I've had some that were very docile and some that were downright homicidal.
The next thing to consider is the earth moving habits of several cichlids. I have never kept a CA cichlid that was satisfied with my decorating style. They will move the substrate around to their liking. So rooted plants are out with them. A lot of Java Fern and Anubias attached to the rocks and driftwood can make a good display with CA's, just make sure that the rocks are resting directly on the bottom glass.
Another beautiful (In my opinion) cichlid group to consider are the Geophagus species. They are big time earth movers, but work well with the Java Fern and Anubias attached to the hardscape. You can break up the substrate with several large rocks to discourage the earth moving habits, just expect them to constantly rearrange the substrate.
Again, to stress the point, make sure that any large rocks in the hardscape are resting DIRECTLY on the bottom glass with any large or medium sized Central or South American cichlids. They will move the substrate around causing minor landslides.
Make sure you do your research on full grown adult sizes, you will be limited with a 30 Gallon tank.