Just make sure you are met by a fairly important person who is well known and can handle any request for 'protocol payments'.
If you are approached just politely refuse and let your contact handle it...like many countries the officials will sometimes try it on...or if you offer they will take...been many times heard stories of having to bribe officials at BUH airport immigration etc. etc. and I have never been asked for anything...same as I've never paid anything in Nigeria!