I've been walking seriously for about a decade now. I've got a dog, so it's mandatory, and my last two locations have been hilly so I'd say I'm doing "good" walks.

I feel great for it, and I'm definitely way healthier than I was when I was younger.

That said, I've found walking hasn't been enough to keep me in shape alone.

It does little to nothing for my flexibility, and whilst it's great for my legs (and possibly core) it does little for strength elsewhere. I also struggle if I need to really get my heart rate up.

Yes.

1) Walk everyday.

2) Vary the pace i.e. brisk walking interspersed with slow walking.

3) Use weight vests/weighed backpacks/ankle weights from time to time.

4) Do uphill/downhill and/or up-the-stairs/down-the-stairs periodically.

5) Walk after Meals and after Exercise.

6) Get up and Walk during breaks in between tasks.