A syllogism gives two statements about groups and asks what must follow. "Must" is the key word: a conclusion follows only if it's true in every situation that fits the statements.
Draw the groups as circles. "All A are B" puts circle A inside B. "No A are B" keeps them apart. "Some A are B" makes them overlap, with at least one person in the overlap. "Some A aren't B" puts at least one A outside B.
Then try to break the conclusion: draw a picture where both statements are true and the conclusion is false. If you can, it doesn't follow.
Two conventions hold in these tests. Every group mentioned has at least one member. And you use only the statements, even when they're false in real life. "All fish can fly; a salmon is a fish" means the salmon can fly, here.
Watch reversals: "All managers are drivers" doesn't mean all drivers are managers.