Don't Mix Up Qing Ming & Ghost Fest. the earlier is a festival to remember our Ancestors whereas the latter is for Unwanted or Hungry Ghosts which's lunar 7th mth.
this year, lunar 2nd mth, mar 9 to apr 6, is Qing Ming fest. actual day is lunar 27th, apr 4. any time within the mth, one can visit the ancestor officially.
if it's buried, one has to ensure the grave & its surrounding are neat including words on the tomb is clear & still readable. if it's in temple, Pray to the Gods first then your Ancestors, cannot be reverse.
at any site, please observe Dress Code. even if it's not mentioned, proper attire is expected. what you wear is a Respect not only to the Gods, Ancestors but Yourself.
at the site, mind your words! a groom-to-be went with his bride to visit her granny's grave. casually he promised that he were sweep her tomb regularly if he were to strike 4D after that Qing Ming session. he won but forgotten the wish. for a few nights he dreamt of her granny asking him When'll You Come to Sweep My Grave? eventually he fulfilled his promise.
as reported in the straits times, some years ago, a family of 7 drowned in a river in guangdong after tomb visit on qing ming day, they might have offended the spirits of the estate by sitting on other people's tombs, spit, urine or pray unwillingly to the ancestors.
due to sentimental reason, other than the Actual Day, any activities eg Renovation, Shifting, Wedding can be done in Qing Ming. your Ancestors is glad you got married, isn't it?
if it's the first Qing Ming for the deceased, the visit has to be done before the actual day.