Click on the edit link in any of the Grand Exchange Market Watch pages, or update in the "Exchange price" section in the item article's infobox (present only if exchange=gemw).
Delete the value in LastDate=.
Move the value in Date= to LastDate=. (Copy+Paste)
Add 5 tildes (~~~~~) to Date= to add the current time/date.
Delete the value in Last=.
Move the value from Price= to Last=. (Copy+Paste)
Add the current market price to Price= (with commas and without k or m; i.e. "42,000", not "42000" or "42k").
If and only if Minimum price = Market price, you may optionally add the minimum price to AbsMinPrice=.
If and only if Maximum price = Market price, you may optionally add the maximum price to AbsMaxPrice=. (The price will never go lower than the Absolute Minimum Price and it will never go higher than the Absolute Maximum Price.)
Please do not intentionally update data on this item in the Grand Exchange Market Watch with false or misleading information, as doing so is vandalism. If you do vandalise this page, you may be blocked.