Clean, uncluttered and well aired are the most important.
Create focal points with big vases of flowers or house plants, sculpture or paintings or photos, not randomly dotted all over the house but grouped together.
Good lighting - lamps, lanterns and candles beat overhead lighting.
Inviting seating areas. I put blankets and cushions on a garden swing and DCs friends always congregate around it when they come over. Same indoors - a log fire on a cold day with seating grouped around it, or sofa and chairs grouped around a big coffee table so people have somewhere to put their drinks down
Fresh scented - not plug-ins or sickly candles but maybe some subtle essential oils or scented sticks as long as they're not overpowering.
In the kitchen, have glasses out already with big jugs of iced water maybe scented with lime or lemon slices, mint or cucumber, so people can help themselves if thirsty. Plenty of soft drinks so people can pace themselves.
If children are coming I always set out a very low table with some safe snacks and craft stuff and toys for them to play with, so grown ups get a bit of time off.