Yeah, from my experience, as far as credit hours go, I would definitely recommend not putting on too big of a load your first semester. try to ease in to it if you have the time. when it comes down to it, pharmacy schools give a much higher weight to your GPA than to how many credits you took a semester. I never took more than 14 credits a semester (but I took a lot of summer classes, which worked well for me, and was another way of showing dedication on my transcripts), and I got accepted to all 3 schools that I interviewed for.
Another few things that have worked for me, that might seem obvious, but still: going to lecture, reading the textbook (i usually could never keep up with the reading, and would end up cramming a lot of the reading a few days before an exam. not the best way to retain information, but it definitely helped me study for the moment), and going to office hours every now and then to talk to my prof. on concepts i don't fully understand.
i'm not familiar at all with your university, but you might want to look into any additional academic resources you might have available, such as facilitation sessions or co-seminars for classes like calc, biology, chemistry, etc. that give you some more support and structured study time for those subjects. i took a few of those my first year in college, and they really helped me manage my time better. skim through any "student guide" stuff you've gotten from the uni, or go on to their website, and check out what tools you have at your disposal. you're already paying for them with your student fees, so you might as well take advantage of them if you can.