Japanese is so efficient as a language that it can sometimes leave new students feeling as though they are floating in space. Without the familiar gravity of shugo (主語, subjects), students are sometimes at a loss to create sentences that involve multiple actors and both direct and indirect actions. This is a result of thinking in English (or another mother tongue) rather than taking advantage of the little tricks that Japanese provides to deal with these situations.
The first rule for using shugo in Japanese? Try to avoid them — if you want to sound natural. For example, take the following perfectly normal conversation:
Q. Sushi tabeta koto aru? (すし食べたことある?; You ever eaten sushi?)