Almost all applications can be done directly through the company application portal. Nevertheless, you might have to do email applications in certain cases.
While doing email applications, make sure to merge all your documents into one PDF and attach the same. Additionally, the contents of your email should be drafted carefully.
Application portals of few companies also engage in automatic CV screening (Application Tracking System) with the help of keywords. In this regard, you should use keywords while filling up the application portal. If your CV gets ranked at the bottom, the system directly sends you an reject and your application will not be reviewed by an human eye.
You should read the job advertisement to make sure that you fit the requirements put forward by the employer. Take into consideration if the position is a mandatory or voluntary internships. Consult with your university to understand if the curriculum requires a mandatory internship. Mandatory internships are usually for a short period and is paid less whereas voluntary internships are usually for 6 months (120 full days) and is paid higher.
Do not keep your phone in silent mode so that you do not miss out on your interview call.