Key information to look for: dates, personal names, conference names, document & publication titles, document symbols, organs where activity occurred (e.g. General Assembly or Security Council), related agencies, etc.
Unlike documents, U.N. publications are catalogued in the library catalogue. Try an advanced search using "United Nations" as an author & some keywords relating to your issue
"Information available for each Member State includes: the key documents related to its membership in the UN; statements made before the principal organs; draft resolutions sponsored; periodic reports submitted on Human Rights conventions, and more."
Contains links to permanent missions to the United Nations for each country
Sites of permanent missions contain foreign government material issued by delegations to the United Nations. Should there be a delay by the United Nations in releasing meeting records or if a better picture of a country’s foreign policy is sought, speeches and policy documents may be found here on the Permanent Mission websites.