The Swiss have so many referendums that they are always on very small, focused issues. Examples from the recent past:
• Should we buy new Gripon fighter jets?
• Should we build a new tunnel through the mountains?
• Should we expel criminals if they are non-Swiss?
• Should the central bank be required to buy gold to back a fraction of the money supply?
Because the issues are so much narrower than referendums in the UK tend to be, it's much easier and quicker to develop an opinion on them.
For people who don't care, they either don't vote (turnout is often ~30% though for the recent highly charged expulsion vote it was more like ~60%), or they vote how the government recommends they vote. Trust in government is very high here so that sort of delegation tends to work OK, and in fact the government wins most votes.
W.R.T. other ways people get informed, it's just the usual mechanisms. Leaflets, media coverage, discussion amongst friends and family. Billboard advertising campaigns notify people of upcoming votes and tend to be very simple. Almost invariably a poster that says something like, "More tax for farmers? NEIN" or "Better working conditions for the people? JA". I doubt they change anyone's minds but they are quite eyecatching.