The first rule about hospitality is not to make any promises that you cannot keep. This said, hospitality can include many aspects, such as:
All these items can be offered
In fact, very few organizations can afford to cover all these expenses, just as very few scholars expect to be refunded for every single expense. What really matters is that you (as well as your call for papers and invitations) are clear and precise from the beginning and that what you promise reflects the level of the registration fee. If you set a high fee, participants expect more, so again be precise about what is and is not included.
If you offer to reimburse expenses, remember to ask speakers to retain receipts or other documentary evidence of their expenditure. This is normally required by sponsoring bodies before they will release funds. It is essential to make clear to speakers what sort of expense you will cover (economy air fares, second class rail fares, no taxis, etc) at the outset. Try to avoid offering to book incoming speakers' travel: this is time-consuming and very unlikely to result in cost savings. On the other hand, conference offices can sometimes book local accommodation very cheaply.
Remember to include regular breaks for tea and coffee, and to allow adequate time for lunch. If possible, a reception at the end of a conference provides an opportunity for more relaxed socializing. Make sure that it is made clear to all participants beforehand (speakers, chairs, delegates) whether their registration fee includes refreshments.
Participants often welcome the opportunity of breaks in the programme to explore the city and its monuments and/or to debate at more leisure specific issues and exchange opinions with individual speakers. They will appreciate finding in their conference package a list of major cultural institutions, events (such as concerts and exhibitions) and bookshops.
These are not only a pleasant distraction but in some case can also present a source of income. They are commonly placed in the hall, or, when possible, near refreshments, so that participants can have a look at books on sale between sessions.