Don't worry, I've got you covered.
The first very important thing for you to do is acquire the role of the correct country. Now, classically the best countries to be are Iran and North Korea, but many fun-hating losers have attempted to ban players from taking these. In addition, most who do not ban them never have the seats open, as anyone would jump at the chance and you're just starting. Do not despair, as alternate, far less well known options are available to you if the role of the Glorious Two are being suppressed. I would suggest you research and then select from one of the following as your B option: Eritrea, Mauritania, Turkmenistan, Myanmar, or Qatar.
Secondly, and this is important, you need to find out the official diplomatic name the Macedonian player is going by. They'll probably be calling themselves the Republic of Macedonia, but it is also possible that they'll be calling themselves the Former Yugoslavian Republic of Macedonia. Your next step will to be to place a call to your nearest actual UN consulate, or if one is not available to the main office in NYC. At this point, you must navigate your way to, depending upon the player's name, the Greek or Macedonian offices. If they're calling themselves the Republic of Macedonia, tell the Greeks about it and express your concerns that a UN-related organization is disrespecting their claims to the Greek province of Macedonia. If they're calling themselves FYROM, call the Macedonians and do the same, except say that the problem is the disrespect of their nation's independence and existence.
Thirdly, you need to stir shit up with whatever chair you've taken. Pretty much all of these actors are excellent choices for spending the entire session making wild accusations of Western imperialism and conspiracy theories while claiming that all of your actions are internal affairs and that the UN as a whole is bound to respect your people's cultural rights. In short form:
-Eritrea locks dissidents in cargo containers to burn to death in the African sun and has no press rights on a North Korea scale.
-Mauritania was the last nation to formally restrict slavery and it still effectively goes on, while also having a cultural fat fetish of force feeding young maidens.
-Turkmenistan is full of weird edicts and has a cult of personality around Turkmenbashi, as well as not allowing any journalism for a period of about ten years.
-Myanmar is just a clusterfuck of militarists and protestors, as well as having an internal naming dispute over Burma/Myanmar.
-Qatar is a hyper-wealthy mini-state with an obscene amount of oil per capita, and most of the population are menial Indian workers who have had their passports revoked and are essentially slaves.
I also suggest, if they exist, that you try to synthesize with the Iranian and North Korean players in order to threaten the West with nukes. Suggesting that the Israeli delegate be permanently disbarred is a good side-project.
Fourthly, either there will already be a host of island nation players, or there will not. If there are, get in good with them, if not, fill all remaining slots with your friends. Land-based microstates are probably also applicable. Finally, get all of them whipped up into a frenzied Carthego Delenda Est-style obstructionism, without fail derailing every topic at hand to complain about how climate change will literally put them all underwater soon. There are a decent number of islanders and microstates when all put together, so if you can convince them to be a bloc over this their sheer quantity will disrupt proceedings nicely. This can also be an area to expand your anti-Western powerbase, on the basis that they are at fault for emissions.
Finally, it is your solemn duty to troll the fuck out of the Chinese player. Now, because you'll be taking such a hostile and devil may cry attitude towards the West and humanism in general anyway you can't take this too far, because backroom deals with the Chinese are important. However, this also makes China a major threat to you, as their burgoning superpower influence can overwhelm your potential for independent action. That is why, while you will throw China a financial bone once in a while about subjects you don't really care about (workers rights, peace movements, etc), you should always take care to perform some high-profile low-impact antagonistic acts as well. Consider hanging up a Republic of China flag in your prep space or leaving boxes of Free Tibet pins around.
All of this taken together, you should have an optimal Model UN experience.