Nothing passes on a tie.
A resolution passes when the number in favour is greater than the number against. Equal is not greater. The same is true of an amendment, and of a clause in a Security Council.
The chair announces the numbers, announces that it has failed, and moves on. There is no second vote to break the tie.
A tie is a result. It is not a fault in the vote and it is not a deadlock. The house has decided.
A close vote may be recounted on request. The chair grants a recount only if the chair believes a counting error was made.
If a recount is taken, delegates must vote the same way again. A recount checks the count. It is not a second chance to change your mind.
If you are unsure. Say clearly, before the recount starts, that every delegation votes exactly as it did the first time. Most delegates who change their vote in a recount do it because nobody told them not to.
The chair refuses the request when the chair is confident the count was right. The chair says so out loud, and says why. The whole house then hears the reason, not only the delegation that asked.
If a delegation simply did not like the result. That is not a request for a recount. The test is whether there is reason to think the count was wrong. It is not whether the vote was close.
If you are unsure. Count again before you announce a result you are not confident in. Counting twice takes seconds. Reopening a result you have already given takes far longer.
These are two different things, and delegates confuse them.
A recount counts the same votes again. Nothing about the vote changes and the result should come out the same.
A division of the house removes abstentions and takes a new vote. Delegations that abstained have to choose a side, so the result can change. It is only valid when the number of abstentions is larger than the gap between the votes in favour and against. It needs a second, and any objection stops it. See Motion to divide the house.
A division of the house is most likely to be moved after a resolution fails by a small margin. It takes a long time, so chairs should avoid it where they can.
If a vote ties after the house has been divided. It fails, the same as any other tied vote.
If an amendment ties. It fails and debate moves on. There is no division of the house on an amendment. See Amendment of the first degree.
The chair gives the numbers and the result plainly, then says what the committee is doing next. Clapping is not in order when a resolution fails. See Clapping and conduct during voting.
If you are unsure. The chair never says whether the thing being voted on is good or bad. That includes a result the chair is disappointed by.
In MEDIMUN, voting happens in MediBook. See Voting in MediBook.