Hello Veena,
The checklist for onsite trips vary with the destination--meaning much of the content is country-specific, even though the general aspects like air tickets, visa processing, etc would be, by & large, common--but those aspects are usually handled by the Travel agents.
Pl give more details like, country, approx period of assignment, type of visa, going with/without family, etc. More the inputs, the better/accurate the members can suggest.
Rgds,
TS