what advice sherlock holmes give to watson, while saying good bye?

The advice that Sherlock Holmes gives to Watson upon his departure to Devonshire was that to simply report facts in the fullest manner possible and leave him to do the theorizing. He did not wish to bias Watson's mind by suggesting theories and suspicions so that Watson could take in the scene in its entirety. Holmes wanted Watson to report anything which may have a bearing upon the case however indirect and especially the relations between young Baskerville and his neighbours or any fresh particulars concerning the death of Sir Charles. He wanted Watson to keep an eye out for all the people who came in contact with the young heir and most importantly, the people in the vicinity which included the servants in the Hall and the neighbours around the moor. The list of suspects would include everyone from the Barrymore couple to the neighbours such as the Stapleton siblings and Mr Frankland of Lafter Hall and one or two other neighbours who would be of special study for Watson as outlined by Holmes.