If you looking for detail morphological and acrosome character, I suggest to use Trypan blue/ Giemsa method dds method for semen smear stain .

Any kind of extraction/isolation/purification of plants and their products you go through the Book Harnborne JB. Phytochemical Methods Chapman and Hall Ltd. New York, 1973; pp.37-214.

It could depend on the species, but after air dried the smaples can wait for staining. In any case, we have publised recent papers on a new technique allowing you to observe perfectly all the sperm structures without staining. The highest importance of this is that you are avoiding the artifeact production inherent to the stainng process.

The techinique is named Trumorph.

Yániz J, Soler C, Santolaria P. Computer assisted sperm morphometry in mammals: A review. Anim Reprod Sci 2015; 156: 1-12.

Soler C, García-Molina A, Contell J, Silvestre MA, Sancho M. The Trumorph system: The new univeral technique for the observation and analysis of the morphology of living sperm. Anim Reprod Sci 2015. 158: 1-10

In my experience (and I do not know why) the brand of the specific commercial Giemsa solution that you use does matter. I have used myself Merck brand Giemsa solution, obtaining good results. Smears can be made with a 7-8 uL drop of semen. You can dilute it, if prefered with PBS. You can quicly airdry your samples (smears), fix them in methanol for 5 minutes, wash them gently with distilled water and then dip the slides in Giemsa (6% commercial solution in distilled water) overnight. I did this with bovine sperm from the epididymis tail. Good luck.

As soon as possible. It not should perform  a log time after preparation  because increase in artefact

If you are trying to determine acrosomal status, is better to use phase contrast microsope if you can access to one. If not, Eosine-Giemsa stain could be good. Tripan Blue has the problem of the incubation (time/temperature) that can make some mistakes in the process. You can mantain the samples for some time when air dried. Of course, as carles said if you can access to a image analyser, you can obtain better and quickly results. As say by Pedro Aponte,  each bach of Giemsa could give you diferent results. You can mantain good images too when fixed with saline-formaldehide solution.We can give you more support if you get as some more information about wath are you doing it for (semen doses production, research, etc)

In my opinion, Giemsa stain differs depending on the company. The best results, in my case, were by using Giemsa from Merck. I let you know the protocol I have used to obtain pretty good results: The preparations have to be fixed before in absolute ethanol and glacial acetic acid (3:1) for 10 min and then they have to be stained in 2% Giemsa (Merck) in buffered saline solution, pH 6.8, for 10 min. You can try it...

This protocol works perfect for me many times!