“We should go for a walk this week” is a friendly agreement. It still leaves two people waiting for someone to suggest a day.
Give that intention a place in both diaries.
Start with one walk you can actually arrange. Choose the day, meeting place and start time together. Add a finish time so neither person has to guess whether this means a quick lunchtime break or an afternoon out.
For example: “On Tuesday at 12:30, we'll meet outside reception and walk for 20 minutes.” The duration is simply a planning example. Choose something that suits both people.
There is research behind making the plan together. A 2012 randomised trial involving UK council employees compared shared planning, individual planning, recruiting a partner without a shared plan, and a control condition. Shared planning showed benefits on some self-reported activity measures during six months of follow-up. Results varied across measures, and simply recruiting a partner did not reliably improve activity.
That is promising evidence for a planning approach. It does not establish that every walking partnership will work, or that this particular lunchtime example is a tested programme.
Make the arrangement together. Ask what time fits the other person's day and what kind of walk they want. If one person wants a brisk session and the other wants a gentle catch-up, settle that before meeting. Both should be comfortable with the plan.
I would also agree what happens when work runs late. Decide how much notice you need and whether to choose another day or walk separately. Nobody needs to wait at reception wondering whether the other person is coming.
Keep the cancellation rule kind. An invitation to move together should leave room for illness, caring responsibilities and an unpredictable working day. Agreeing a replacement time can be enough; there is no need to turn a missed walk into a debt.
After the first attempt, check the arrangement. Was the meeting point convenient? Did the timing fit? Did you both enjoy the pace? Change the detail that got in the way before booking another.
Finish the conversation with a walk both people can picture: where you'll meet, when you'll start and what you've agreed to do together.