Be ready early
WebMD explains that about half of twins are born before 38 weeks gestation [1]. If you are putting off baby showers or baby proofing, consider starting now. You don't want to be buying car seats the day of your babies' birth.
Two is not always true
It is said that if you have twins, you're going to need two of everything. This isn't always the case. Learnvest suggests that you look at the options. If you use unisex onesies and share things like the baby bathtub, you can use them for both babies. Also, try and wait to buy the things you'll need two of (highchairs or cribs) until they absolutely need them. By doing this you are spreading out your payments and giving yourself more time to save [2].
Think about child care
Once your maternity leave ends, someone is going to have to watch the babies while you're at work. WebMD explains that daycare costs about $1,200 a month and over the year can equal an after tax salary of about $30,000. Think about this and decide if it might be more cost effective to have a parent work part-time or just stay home altogether [1].
The little things add up
Think about all of the little stuff that you are buying that adds up. For example, it might be cheaper for you to buy a food processor and make homemade baby food than continually buying store-bought food. Or things like baby shoes-though they seem cute, they aren't really necessary until the baby is walking. If you can resist, try and stick to socks [1].
Save now
Now that you have two more people to worry about, you should put more money away in your emergency fund. Saving for a rainy day early will help you when something goes wrong. Saving today will help you better handle troublesome situations in the future [3]. Also, consider stating to save for college now. Even putting away a little bit of money each month can add up over 18 years.
Check for deals
Wisebread explains that there are many stores that have acknowledged the necessity of having options for parents with twins, and have begun offering discounts. In an addition, Wisebread suggests taking advantage of the niche discount only available to parents with twins [3]. Also, ask friends or family if they have anything they'd be willing to give you. Usually people are very happy to see old baby clothes get used, so don't be afraid to ask.
Sources:
[1] Budgeting for Twins: Tips to Save Money
[2] Raising Twins: 7 Financial Costs to Consider
[3] 7 Lessons About Money I Learned After Having Twins, Wisebread