With a host, the host guides, the gentleman follows and if there is room to maneuver, the gentleman's guest would be at his arm.

If the guest is someone in business or another gentleman who is not a significant other, that guest would follow the gentleman.

If there is little room to walk side by side and the guest is a lady, she would follow the gentleman closely and he should consistently tend to her in making sure she is right behind him all the way.

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When there is no host and it is 'seat yourself', the gentleman would still take the lead in all the same respects as if there was a host.

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Upon arriving at the table, a host would appropriately hold the chair and seat the lady first while the gentleman remains standing. In some venues the host will then seat the gentleman if the fellow hasn't begun to seat himself already upon the lady being seated.

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Such proprieties extended by a host are not so common these days. Truly unfortunate as there is a real beauty and grace to etiquette.

It's very nice of you to ask