Reaching out about renting a car in Ireland

Try https://www.autoeurope.com/ as a starting point.
If you have any memberships (AAA, Costco, USAA, etc.) you can sometimes get pretty good deals by booking with them.
Make sure you understand the insurance cover in order to get a true apples-to-apples comparison of the total price.
And you'll need to specify an automatic if that's what you want or require. The default rental in Ireland is a manual shifter.
We've always used Hertz in the past with no issues.

I’m leaving for Ireland in three weeks with my cousin. She rented a car however, as I have been reading it sounds like you need a special insurance policy or something while renting there or you could be stuck with a large bill when you arrive. Does anyone have any tips or suggestions for this?
Thanks

I think it depends where you are driving. The main highways are fine and I would only get the "usual"
insurance. But if you're going into the small towns, especially out in the west and southwest, I'd go ahead and spring for the total coverage. Mind you, it's ridiculously expensive - probably will double the cost of your rental. But it's worth it for peace of mind. Just came back after 2 weeks driving in country roads, lanes that were not wide enough for 2 small cars to pass without both cars scraping along the bushes that line the road. Mind you, we loved it. But having the total coverage made it a lot
less nerve-wracking. And, as everyone says, DO NOT DRIVE in Dublin. Crazy. We used Avis. They were fine.

We picked up the car at the airport, drove out of town to Kilkenny and then did our thing through the west/southwest. We dropped the car off at the airport, then took a cab into Dublin and did not need a car there. Went via cab back to the airport. The major highways outside of Dublin are very much like the U.S.

And, as others have said, get an automatic. I had no trouble driving on the "wrong" side of the road. But having the shift on the left side of steering wheel would have been very difficult for me to get used to. My guess is that it's a lot easier to reserve an automatic during the low or shoulder seasons than it is in the height of the tourist season. We went from mid-October to early November. Have a wonderful time! You will have a great experience.

How early did you all reserve your cars? Is it something you can do when you get out there, or did you reserve in advance?

I've always rented a car in advance. I think it's cheaper when coming from the US. I don't think you have to reserve too far ahead of time, a couple of weeks may be fine. I usually check the price a few times then take time to read the small print before booking. Lately I've noticed a lot of language I don't like (e.g. "a drop charge may be added") but not disclosed in the price quoted.

If you can drive a stick, it's not that hard to adjust to the left side. If you don't normally drive a stick, you probably want to reserve an automatic. Generally an automatic costs quite a bit more (but not always) and gets less mileage than a stick.

I've used Thrifty and Hertz recently. In the past, I've used Autoeurope and probably some others. I haven't really had an issue with any of them except I was charged a drop charge by Thrifty last time (picked up in Toulouse and dropped in Bordeaux).