Bethune College is one of the renowned colleges in West Bengal. As you have opted for B.Sc Economics One of my friends also studied at Bethune College, so I might be able to provide some tips about this:

• Buy a last 5-year question or CBCS system previous year’s question as soon as possible. 
• Calcutta University tends to give the same question in an odd-even-year system. Solve those papers and prepare accordingly as 60% of the questions will be similar.
• Make sure you utilize the profit of the online exam system. You can score 15-20% extra than offline exams. 
• After the regular college classes if you need extra guidance to go for a coaching centre suggested by your seniors.
• Keep in touch with your seniors frequently, as they can guide you through a lot of things.

Lastly, as Bethune is a very strict college, try to enjoy your college life, maintain a good relationship with your teachers and work hard and study well to make a successful career.