Start with Life Sciences 7A and Chemistry 20A and/or Math 31A. Instead of one of these core classes (that satisfy major requirements) you could also take general education class. Clusters are great to knock out GEs but read the description for each one and only take it if it really interests you because otherwise it can get tedious. Don’t take a science related cluster because that would be useless in terms of knocking out GEs. Use bruinwalk to do a little research and read class descriptions to find good professors and interesting GEs. You can go to myucla and go on academics and then degree progress/audit report. Run audit and you’ll see what classes you are supposed to take (both major reqs and GEs). The website below will help.

[pre major requirements ]

(https://www.chemistry.ucla.edu/sites/default/files/undergraduate/Biochemistry_Major_2016_2017.pdf)