You can take a drop of culture then fix and stain by Geimsa and observe by light microscope. If wanna observe alive cells you may use an invert microscope and take the clips or pictasures as well.
If you have an eppifluorescent microscope, you can use Sytox, which is a fluorescent stain that permit to observe amastigotes nuclei inside macrophages and in addition allows to detect macrophage's nuclei
As Mr Abbas Ali Eskandarian answered, the light microscope and a Giemsa stain is the best. It is (or until recently) the official diagnostic observation. More sophisticated techniques are interesting, but this basic one is just perfectly functional.
I couldn't resist posting this as an example of staining used for viewing the amastigotes of Leischmaniasis. This was taken from my arm in 2006 (after I was bitten by a sandfly in Panama in 2005).
[This post officially ranks as the worst --and most personal--contribution on ResearchGate.]
We use to work with intracellular parasites inside of macrophages(some of my papers are in internet. Of course giemsa stain is the best, but for membrane destruction or things like that you have to use electron microscope or biochemistry tests.