You do not speak for yourself in a committee. You speak for a country. Everything you say in the room has to be something that country would say. That only works if you know the country first.
Start here, before you read anything about the topics. A delegate who knows the country can work out a position on almost any issue. A delegate who only knows the issue cannot.
Work through these in order. Write the answers down somewhere you can open in the committee room.
The basics. Full official name. Region. Neighbours. Population. Languages. Capital.
How it is governed. The system of government. The head of state and the head of government, by name. When the government last changed. Whether the current government is likely to change soon.
Where it sits. Membership of the United Nations and of its agencies. Membership of regional bodies and trade groups. Military alliances. Which countries it works with most closely, and which it does not.
What it lives on. The main industries and exports. The main imports. Who its largest trading partners are. Whether it gives aid or receives it.
Its record. Treaties it has signed, and treaties it has refused to sign. How it has voted on your topics in the past. Statements its representatives have made at the United Nations.
Its own situation. Whether the problem being debated exists inside your country, and what the government has done about it at home. A country that has the problem itself argues differently from one that does not.
Use the country's own government websites and the website of its permanent mission to the United Nations. Those tell you what the country says about itself, which is what you have to represent.
Then use United Nations sources. Country pages, agency reports and the records of past votes.
Then use reputable news reporting and academic writing to fill in what the official sources leave out. Check the date on everything. A position from ten years ago may have been reversed since.
Artificial intelligence is not a source. It may be used as a tool to help you, where your own school allows it. Everything it gives you has to be checked against a real source before you use it. See Plagiarism.
Your job is to represent the country accurately. That includes representing positions you disagree with. If you argue for what you personally believe instead, the simulation stops working. The room is then debating a world that does not exist.
Keep two notes on each topic. What the country's position is, and what the evidence for that is. Your own view does not go in either.
If you are unsure. When you cannot find an explicit statement from your country on a topic, reason from what you do know. Its alliances, its economy, its past votes and its own domestic situation will point one way. Say what your country's interest is, rather than inventing a quote it never gave.
Say "Less Economically Developed Countries". Do not say "Third World Countries". This applies in your speeches, your position paper and your resolutions.
In MEDIMUN, countries are granted to schools, not to individuals. Each country a school is granted gives it one delegate seat in each General Assembly committee. No two schools share a country. See Delegation applications.
If you are in a Special Committee. You will usually represent an entity rather than a country. Research its mandate and its founding documents in place of a national interest. What it is allowed to do matters more than what it wants.
A delegation that is not a member state still has full voting rights. Non-governmental organisations and United Nations organs vote on amendments and on resolutions in the same way everyone else does. See Who may vote.
If you are unsure which committee you are in. Check in MediBook before you start researching. A Security Council or a Special Committee may need different research from a General Assembly committee. Finding that out late costs you preparation time.
Once you know the country, move on to the topics. See Researching the issue.