Identify top 2-3 verticals of interest: this helps narrow down your scope in the wide energy & sustainability industry. Some verticals include oil & gas, mining, wind energy, geothermal energy, renewable energy (overall), solar/photovoltaic energy, nuclear power, etc.
Build your functional skills: as mentioned by the Fuqua School of Business EDGE Notes, energy companies are looking for specific skills in finance, operations/supply chain, decision sciences, and marketing/sales.
Understand concerns of key stakeholders: Read 1-2 brokerage reports on your target energy segment or potential target companies, and identify key products and trials investors are monitoring
Dig deeper into technical trends: Every month, check (or if you dare, subscribe) to industry journals like Oil & Gas Journal. Knowing some industry nuances may impress an interviewer at the right time, and/or a future boss.