Target audience

You're a current software engineer for a tech company in the United States.

Some tips are relevant for any role.

Timing

Seasonality

Larger companies tend to set headcount (number of new hires per team) annually, so team selection is often most flexible ~Jan-March.

Hiring is slowest between Thanksgiving and New Year's Day, and slows down a bit over summer.
The economy / funding environment

Since I became aware of tech companies, around 2014, it seems like tech hiring has only gotten hotter and salary packages have also grown, aside from a brief lull in Q2 2020.

However, there were definite busts in 2000 and 2008 during which it was harder to raise funding in the private and public markets. As a result, finding a job got a lot harder, especially without previous experience, and salary packages were lower.

How is your current job going?

Out of scope but obviously a critical question to answer when deciding whether to leave.
How long have you held the current job?

If under 1 year, only leave in case of ~emergency, as it's unusual to leave before hitting your 1-year equity cliff, especially at larger companies. It might look like you were fired.

If 2-3 years: what does your career look like at this company? Are you close to getting a promotion with a title bump, to Senior Software Engineer, for example? If so, you may want to stay until just after the promotion.

If 4+ years: are you still learning and growing? If you're growing quickly along with the company, congrats! If not, consider at least looking around.