[susan53]

Sorry - I didn't see the second set of questions when I answered before. These are easy - are you talking about a permanent fact :

Every time my friends and I go fishing, we catch a lot of fish.

or a past event :

I had a fishing holiday with my friends last year and we caught a lot of fish.

Your comment seems to indicate that you mean the first. So :

I often go fishing with my friends. Sometimes we catch a lot of fish. Other times, we don't catch anything.

But if you are talking about the past :

I had a fishing holiday with my friends last year. Sometimes we caught a lot of fish. Other times we didn't catch anything.