What should I do before I start fıtness?

I have never done work out what should I do befoe I start my fıtnees program? It's recommended to walking regularly for 2/3 weeks but ıt has no detail
how many days a week will ı walk? how fast? how many minutes? and is it walking or running? ıt says walking but running sounds more suitable
What should I do before I start fıtness?
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