DK's Chronicle of the 20th Century (Book or CD ROM) would be a good place to start looking.
Those videos sold in card/gift shops which summarise a year or decade might also be a good source of information. Other than that - ask your friends what they were doing in 1990
1990 was a hot summer, I was getting thrashed around the countryside at the time and nearly copped it with heat exhaustion. Adamski was a big hit with Killer and hearing that now makes me feel sweaty. Then Saddam invaded Kuwait in August and we all held our breath. News of war in Iraq dominated the news big style until Feb 91.