If you're not married (you say partner so I assume not) consider the legal and financial protection that it provides and decide whether you want to get married; it's much more difficult to do it after you've had children. This may not be so important to you if you have a good career and intend to share parental leave, return to work full time and share the load in terms of childcare/school drop offs and pick ups, time off when children are sick, etc. However, many mothers end up making a bigger sacrifice in terms of their careers, earning potential and pension contributions, in which case marriage is pretty much essential protection.
Talk to your partner about expectations in terms of sharing childcare and housework duties, whether you have any strong feelings about how you'd like to raise your children (eg religion, state/private school, anything else that might be important to you), how many children you'd ideally like (one or both of you might change your mind about this later but it's worth checking in now).
Ideally you'd be living in secure housing and you'd do DIY and decluttering before baby comes, but plenty of people manage in less than ideal living situations, it'll be more stressful to move or renovate later but it's doable.
You and your partner should both stop/reduce alcohol intake while TTC; it's not just the woman who has to be careful about drinking. Of course once you get pregnant he's done his bit and can then drink again but he might want to do so in moderation in solidarity with you!
If you're not already reasonably fit, try and get fit before getting pregnant, as it will make pregnancy and childbirth easier. Ideally you'd do Pilates to strengthen your core and reduce the risk of getting PGP (I wish I'd done this but hindsight is a wonderful thing!)
Check out the Positive Birth Company or similar antenatal courses. Consider getting a doula to support you at the birth if you can afford it. As a first-time mother, the midwives might not take you seriously; remember it's your body and you make the decisions (albeit on listening to medical advice).
Don't tell anyone in real life the name you've chosen (or the names you're considering); keep it between you and your partner and wait until baby's born before announcing it.
Give baby your surname.
That's all I can think of for now but I'm sure there's loads more!