Formal:
* Affably: This is a good synonym if you want to emphasize being pleasant and easy to talk to.
* Cordially: This implies warmth and friendliness.
* Graciously: This suggests polite and kind behavior.
* Kindly: This conveys a sense of gentleness and goodwill.
Informal:
* Cheerfully: This implies a positive and happy attitude.
* Warmly: This conveys a sense of affection and fondness.
* Pleasantly: This emphasizes a positive and enjoyable experience.
* Nicely: This is a simple synonym for "amiably" that works well in most situations.
Other synonyms:
* Agreeably: This emphasizes a sense of agreement and harmony.
* Good-naturedly: This implies a kind and forgiving nature.
* Sociably: This suggests being outgoing and enjoying social interaction.
The best synonym to use will depend on the specific context and the desired nuance.