There is the well known specific gravity test that is often used, and that is described somewhere on the site I think. The method I am showing is for when an object is mixed metals, or of a shape that does not let specific gravity work well ( air bubbles etc.) . It is very slightly destructive, if the object might be of great value then better not - it is to test unidentified odds and ends that might have gold in them more than anything.
The traditional broker method of this uses strong acids, and is harder to buy. Here the ingredients are common and available. I don't say it is foolproof as maybe some metal alloys will not react and seem like gold, I have only tried on a few of bronze and brass - so it is a work in progress and anyone might chip in afterwards anything they discover with other metals.
The method is to polish some metal onto very fine sandpaper, here I used 500 grit (from weber I think) - you will have to find similar which holds up to the test.
You then prepare a mixture of jewellery pickle ( used for cleaning jewellery when it is being made - don't try to clean coins with this!) . The original recipe is slightly different ratio, but simplest is 50:50 of hydrogen peroxide ( h2o2 at 3% strength) and vinegar. Hydrogen peroxide must be kept out of the eyes, wash immediately if you splash them ( i.e. don't splash it around).
You then dab on this mixture lightly to cover the metal trace on the sandpaper. Usually it dissolves other metals quickly, but we'll leave it to dry to examin more carefully afterwards. Use a torch or light source to look if metal reflection still exists on the streak afterwards.
The photo shows original item at top.
Left to right is : 22k gold (drawn, as no original image available), 9k gold ring, brass ring that might be gold, another thin brass/bronze ring that might be gold, a bronze or brass weight, a copper based coin probably brass.
Below that is the streak after made.
Below that is just after mixture added.
Below that is how it looks when dry.
So no disappointment there, only the objects known to be gold actually showed as being gold.