As a first time mother of a 4 month old baby, I've learned so many things about taking care of a baby. However, there are certain things I wish I knew so I could make a better decisions about some of these things early on.
1. Flat Heads 
Every reading source and and health professional would tell me to put my baby on his back to prevent SIDS (Sudden Infant Death Syndrome). What they didn't tell me is that this can cause flat heads. I noticed my baby started getting a flat side on the back of his head when he was around 7 weeks old. I was really paranoid about it and talked to my pediatrician about it at his 2 month check up. He said that it's not that rare to see this happen to babies and if it gets worse then we can get a helmet for him. He says it would be around $4,000 for that and encouraged that we give him more tummy time. He said it isn't bad enough yet where he would recommend the helmet so I've been trying to give him as much tummy time as I can. It's usually only around 10-20 minutes a day now because he learned to flip over around 3.5 months old. I suggest putting him on a boppy pillow for tummy time if your child can already flip over. It prolongs his tummy time. It's been 2 months now since my last Dr. visit about his head and it hasn't gotten worse but it hasn't gotten better either. We have an appt. in 2 days for his 4 month check up so I will see what he says.

It's definitely a new generation problem because I didn't have that problem as a baby. Back then, mothers were encouraged to put babies down on their tummy. Within the last 20 years, it has been changed to put them down on their back. 

2. Giving babies a bath every other day is too many.
According to my baby book, they said to only give babies a bath 2-3 times a week. I didn't take it literally and gave my baby a bath every other day which translated to 3-4 times a week. Even though it's one more bath than the recommendation, it is still to many baths! It started drying out his skin and then he would get itchy and develop rashes all over his face. It started with his face because it's the most sensitive part for skin of the human anatomy. Then he started getting them on his arms and legs. He started getting them around 6 weeks. I blamed it on maybe he was allergic to the dog at home. Then I blamed it on Johnson and Johnson shampoo. And then I blamed it on the lotion and the weather. After 2 months, I finally figured maybe I am giving him too many baths and it zapped all of the moisture from his body. Even though maybe he could be allergic to those other things, giving him too many baths really dried out his skin. I went to the doctor 2 times for these rashes and he said that babies develop rashes and it just takes time until they get used to the environment. He didn't mention anything about my baths but I've cut it down to the recommendation and his skin is so much better! 

3. Get a cradler for the car seat. 
We probably take the baby out for a car ride about every week or so. Occasionally, it would be more when we go on weekend trips. Whenever he would fall asleep in his car seat, his head would slump forward and it freaked me out! I would put a blanket or my hand on the side his head would slump to make it more comfortable for him. What I didn't know is that they invented these things called cradlers that helps support his head so he doesn't slump. I didn't find out until just now, 4 months later! So get those cradlers ahead of time so your baby's head is more comfortable. I'm not sure if these have caused any suffocation instances so maybe you just make sure someone is right beside the whole time during the ride. 

These are the 3 main things I knew early on so I could prepare for better care for my first born. I hope this helps you as well!