Conventions found in Trailers

Typical conventions of soap opera trailers

The storylines in soap opera trailers are always hinted at and not shown in their entirity; this helps ensure that audiences remain curious and watch all episodes rather than just find out what is going to happen from a trailer and then maybe skip certain episodes. The storylines in trailers are also quite big and theatrical; trailers arent shown for just ordinary episodes, they are normally for murders, marriages or a popular or well known character returning or leaving.
Quite often trailers only feature a few characters who are central to a particular storyline and don't show all of the others. This is because the trailer gives the viewer hints at what will happen in the actual episode and so the audience feels like they are more involved because they are trying to work out what is going to happen. This goes against the idea of the "hyperdermic needle theory" where audiences are passive and don't participate in the program, they just sit back and accept whatever is given to them.

The conventions of a full episode differ slightly. Quite often an episode will feature several different storylines at once, normally making use of "real time" where a soap doesnt skip out huge sections of time. Having several different storylines going on at once is a good way of keeping audiences interested and improving viewer ratings, because there is more going on.
Also, most typical epsiodes won't all be extremely theatrical, and will center around more mainstream things, or things that viewers can relate to. If a soap has explored a certain storyline that they think will have affected people in the audience, a telephone hotline number is often displayed at the end.