Firstly, you will need to do some homework like gathering shortlisted hotel related information or all hotels related information if no idea where to hold your wedding.
Then, you consider the below:
1. Within your budget?
2. Location?
3. You like the place & atmosphere?
4. Perks good?
5. # of tables you have
Of course, after you shortlist the hotels, visit them with a camera and take photographs for discussion use.
After then, gather all your thoughts and photo while discussion with your partner.
Once confirm of booking that hotel, go together with your partner and start bargaining.
You have to know what other hotel offers, then you can ask why this hotel don't have and ask if hotel could provide the same as what other hotel offers ... etc