by 1- boiling water  2- by ethanol or methanol extract  3- by acetone, the best solvent  4- by hexan when mix solution between polar and non polar solvent (hydrophobic and hydrophelic solvent). 

Yes, you can also try different extraction techniques - e.g. classical liquid-liquid extraction, sonication, microwave extraction, etc. On the other hand, you can also prepare extracts in different solvents (as is it suggested above) or prepare one (e.g. water) and fractionate it between different solvents. There are many approaches, you can choose. Good luck!

The extraction can target non-polar, moderately polar or polar components. This means you can use different solvents starting from less polar solvents like hexane to highly polar solvents. In most cases three different solvents (e.g. hexane, ethyl acetate, methanol) are used. The assumption is that hexane gives all the non polar compounds, ethyl acetate gives moderately polar compounds while methanol gives polar compounds.  

For phytochemical screening I prefer sequential solvent extraction from low polar solvent like hexane to highly polar methanol

Hi Kumar! 

I suggest you make an extraction with solvents of increasing polarity. I used to use in first place hexane, then benzene, ethyl acetate and ethanol.

Regards!

Thanks to all of you for kind Information

The extraction method (solvent and condition) depends of the type of compounds that you are looking for. If you are bioprospecting or following a bio-guided method is convenient apply an exhaustive extraction (i.s. dichloromethane-methanol). But if you are looking for specific compounds, you must be careful with the extraction conditions. For example, for volatile and labile compounds (i.e monoterpenes) in the extraction, you must avoid concentrate the extract using heat, and in the storage must be free of light and oxygen. Other typical case for metabolite targeting is with alkaloids, you can maximize the extraction of alkaloids using the acid-base properties of this compounds, and you can obtain high yield and upper purity.

Here there are a brief and concise explanation: 

http://disruptechno2.free.fr/FMS/Natural%20product%20isolation%20(Otto%20Sticher).pdf

I will prefer a sucessive extraction  from non polar solvent to mediumly polar and finally to highly polar solvent using cold extraction method to avoid denaturing of heat labile metabolites present in the extract

thanks Melendez

I suggest you to perform soxhlet extraction for the preparation of plant extracts. because in this method you can obtain high yield of extract. 

Ya true, i  totally agree with Claudio. extraction process depends on your compound of interest. Well, there are a lot of techniques as said by previous authors. 

There is one beautiful article by Italian ministry. just check

https://www.unido.org/fileadmin/user_media/Publications/Pub_free/Extraction_technologies_for_medicinal_and_aromatic_plants.pdf