Like any good traveler I am immersing myself, as best I can in the local culture. Since coming South from Brazil, one of the staples in the cultural and culinary diet is the consumption of Mate. (Pronounced Mat-eh. Like your from Leith.)
Mate is not just the humble tea we are used to in Britain, it is a ritualistic right of social passage whose fiercely contested practices vary from country to country. Sometimes causing war. (Note- No wars have started as a result of Mate.)

History
Originally, an indigenous Paraguayan drink gifted to the people by the Goddesses of the Moon and the Cloud, it was soon adopted by the conquistadors and more recently the Gauchos, south american cowboys of the pampas region who used the drink to get pure buzzin. Now it is the buzz water of choice for most of Argentina and Uruguay and is still widely consumed in parts of Paraguay, Brazil and Chile.
The processes and practices around the consumption of Mate is where  contention lies. The resultant drink of the differing methods is generally a hot, quite bitter, tea with high caffeine content however even this can fluctuate.
Equipment
Confusingly, two parts of the Mate kit needed to drink the Mate share their name with Mate.
Firstly, the Mate. This is the cup which holds the drink. Like human beings they come in different shapes, sizes and colours. Unlike humans they can be made from metal, wood, plastic or horn. Most traditionally though, the seed of local plants are hollowed and cured with hot water and yerba and then used to drink from.
Which brings us neatly to the yerba mate. This is the tea. It is dried and chopped leafs from the ilex paraguarinesis or something like that. Each yerba is different in strength and taste with some boasting different health properties such as digestion aid or high antioxidants.
Next you will need aqua caliente or hot water. This is a contested point as some people use boiling water some insist the water should be around 80 degrees or so. It can come straight from the kettle but often is stored in a thermos, like you really care. Incidentally, the ingestion of hot water may increase your chances of some cancer types.
Lastly, the bombilla. Or the straw. This is usually a silver, cheap metal or wooden pipe at the end of which is an attached seiving device. Often a percolated chamber, sometimes a spring. Exciting.
Controversial additives include sugar and other flavoured herbs.
And if you so desire you can add cold water or orange juice and make yourself a térere. That’s like a mad, cold version that exist in Paraguay and Brazil.
Lastly, please do not worry, you can get most of your Mate equipment tackily personalised with your name, your country or your favourite football teams logos.

Consumption

After that riveting and poorly researched history and equipment guide, it’s time for the consumption lesson.

Having filled with water, drink Mate through the straw.
If only it could be that simple.
Some argue never add sugar but if you want sugar add this to your Mate first. Next add the yerba, this should be briefly shaken to remove dust and then allowed to settle with an angular face in the Mate. Now, insert the hot water, pour it over the side with the gap. Lastly, with your thumb covering the hole, insert the bombilla sieve side down into the same side you put the water. 
As you drink more, allow more of the yerba to be moistened by the hot water. If you are drinking alone that’s it, you fucking did it!  Just try now not to get too buzzing.
If you are drinking in a group, you are just starting.  God help you. 
Infact, there are so many social faux pas to be commited I can’t even begin to describe them all. And of course they vary from country to country. The basic idea is you will receive the Mate, drink the Mate until it is empty then pass it on. 
Whatever you do, just don’t pass the Mate on to the wrong person, or pass it on unfinished, or add your own sugar, or serve it to yourself if someone else started serving, or touch the straw, or say thanks if you want more, or…
You get the picture. Wherever you are though, congratulations you have taken part in a social custom that bring people together with a close ritual which bonds people as well as the similar passing and smoking of joints except with double the motivation. If you are drinking alone, you’ve got no Mates. Get it Hahahahahahahahahahahahahahahahahahahahahaha.

Mr Hummels