It is highly recommended that you join a scientific society as a student member. Most societies (e.g., Society of Toxicology, Society for Neuroscience, American Society for Pharmacology and Experimental Therapeutics, American Society for Pharmacognosy) have reduced rates for students, allow members to apply for travel awards to conferences, provide job search opportunities and offer other benefits. Societies are one means to be involved as a steward of your discipline and gain exposure to valuable opportunities.
You can also find a journal club on campus whose research interests are closely aligned with yours. The molecular and cellular biology program runs a journal club every Friday. A journal club for those interested in receptor pharmacology meets twice monthly. Other options may be identified by your major adviser.
There are also other ways to get involved in shaping the department and the future of your discipline. The graduate studies committee has a student member. Graduate students are always asked to meet prospective faculty at interview lunches and to provide feedback to faculty search committees.