When I was preparing, I found all kinds of crazy examinations of conscience, but the most helpful were the shortest. I carried
this one around with me for the first few months.
If you want to go even simpler, pray over the 10 commandments, plus
Love your neighbor as yourself. You don’t need to make an exhaustive list of venial sins. Just ask the Holy Spirit for guidance and to help you make a good confession. He will. Also, if you get stuck, ask Father to help. He will, too.
If you want to push the envelope… while you’re preparing ask,
Jesus, what do you want to hear me say to you? In the beginning, I found this helpful because it was a very firm reminder of who I’d be talking to in there – it took care of a lot of anxiety. As I moved forward, the answers to this question have often resulted in seismic shifts in my relationship to God and his Church. It keeps things interesting.
Most of “what it was like” for me won’t be relevant for you, because I was making a 15+ year confession, and you only have to look back a month. But the priest was kind and patient, and I trust you’ll be able to expect the same. A couple dozen confessions later, 1. I’m still going!, 2. the words of absolution are always an enormous relief, and 3. receiving Communion when you’re fresh and clean like that is awesome.
I’ve prayed for you, that the Lord will help you make a good confession, and give you abundant assurance of his mercy.