Is having tequila on the rocks OK? I like it that way with liberal squeezes of lime, though in that case I realize I’m not drinking tequila anymore, but a mixed drink of tequila and lime juice.
Whatever you like. I wouldn’t drink a super-premium tequila that way. But I don’t drink super-premium tequilas unless someone else is buying.
The Paloma is an excellent non-fussy way to drink tequila.
I prefer to add more lime juice. Some recipes recommend fresh grapefruit juice & soda. Salt? Not for me, but some like it.
I agree with the last part, but your roommate, while he has the right idea, is drinking the wrong tequila.
My last job before this one was in a tequila bar. At that job I learned that price is indeed a good indicator of quality, but there are many brand-names (notoriously those exact two that you mentioned!) which inconsistent in quality but quite consistently overpriced. I have found that most of the tequilas worth that kind of money are a little harder to find.
As to the OP, here are some rules that I follow in tequila-drinking:
1) Stay away from Cuervo.
Really. They make only one decent tequila, and I promise you you can’t afford it.
2) Stay away from anything which includes the word “GOLD” in its name.
This basically means they have added caramel coloring and additives to the tequila to make it appear aged. To you this means bad taste, and a horrible headache.
3) Buy 100% El Agave tequila whenever possible.
This is not a brand of tequila; it indicates what is in it. This ensures your tequila is distilled properly and not full of additives that do nothing for flavor or sensation.
4) Use fresh-squeezed lime juice (as opposed to a pre-packaged mix) whenever possible.
I cannot tell you how much this will improve the flavor of your margaritas. Fresh limes beat the HELL out of sugary mixes and concentrates for both healthiness and flavor.
5) Do not use Anejo tequila for margaritas or shots.
Anejo tequila is not made for gulping; it’s aged so long that it takes on an oakiness and strength of flavor very much like a bourbon. Besides that, most of it worth buying is too expensive for margarita-making. Stick with Silver and Reposado (my favorite).
As for an exact recipe, those can vary. I usually eyeball it: I put about a shot of tequila (more if you really like to taste it), a shot of orange liqeuer (Cointreau is my personal favorite), and then fill up the glass with equal parts lime juice and simple syrup. Salt if you wish.
I don’t know if you’re looking for particular brands, but some of my favorites are as follows, from cheap to expensive: Sauza Hornitos, Milagro, Buscadores, Corralejo, Corazon, Espolon (absolute favorite), and El Tesoro.
Hope this is helpful; have fun 
sacrilege?
perhaps. I had a friend make a pitcher of margaritas in the blender. He put in half as much ice as you normally would for frozen margaritas, and added almost a can of lager beer as well. Wow, very tasty!
I cannot speak with a louder or more authoritative voice than those that have come before me.
And yet, this is what I do:
8 oz Hornitos Sauza (medium cost, stellar taste)
2 oz Cointreau
3 cups Margaritaville mix (notice a similarity to the OP? There’s a reason.)
Lime juice to taste
Salt
Rocks.
Otherwise, here’s the frou frou stellar sister:
6 oz Sauza Hornitos
1 oz Cointreau
Mr & Mrs T’s strawberry marg mix
Frozen strawberries to bring it up to the ‘2 serving’ line.
Blend til you do through a blender a summer
Drink will come out as a slushy, with frost wafting over the side. The second drink will make your lips numb.
I know the Patron brand is highly popular, but I’m partial to the Don Julio varieties. The añejo is too expensive and complex to be wasted in a mixed drink, IMO, but the Don Julio Silver (in the area of $40/750ml) is a 100% blue agave tequila that I found quite smooth and drinkable straight in addition to being a great margarita ingredient.
In the spirit of discovery, one night I drank a shot of Don Julio Silver followed by one of Sauza Hornitos— the latter was so rough by comparison that I nearly choked. Despite all the marketing, I’ve never found all that much difference between cheap and ultrapremium vodkas (when chilled to equivalent temperatures), but a fine tequila is unmistakable bliss compared to its rotgut pretenders.
Believe me, as a veteran of more than one high-end tequila tasting party, nasty, painful hangovers are by no means restricted to imbibers of cheap tequila.
brrrrrrrrrrrrrrr
Recommendations of some brands I’ll find in my local state-run liquor store?
I’d like one to sip, but also one for margaritas. Would it be a sin? (I.e., I don’t use 12 year old Scotch when I make whiskey drinks. I also don’t make whiskey drinks.)
Sure there is. It is for doing things that astonish you the next day, without feeling “drunk”.
Course not. There are many tequilas that meet this standard, but how many of them you’ll find in your local state-run liquor store, I don’t know.
Patron is a 100% El Agave tequila, and that one you will find in any liquor-selling establishment with a roof. I don’t recommend it, personally, but a lot of people like it. My issue with it is that the agave isn’t consistent from one batch to the next, because (correct me if I’m wrong) they don’t grow their own, and don’t buy from just one source.
Don Julio is also pretty ubiquitous. I’m not crazy about this one, but I’d rather drink it than Patron anyday. It’s high-quality and there’s nothing wrong with it; I just don’t find it particularly remarkable.
Sauza Hornitos is another one you should be able to find anywhere. I do like this one a lot. In fact I drink this one more often than anything, because it’s really fairly priced for an aged tequila and it’s got a great flavor for margaritas. I wouldn’t necessarily recommend sipping it… but then, I’m not a big sipper.
Herradura is easy to find, good quality… a little pricey, but it’s about on par with Don Julio and Patron. I don’t like the silver all that much (it’s a little bland for my taste in margaritas, but very easy to shoot), but the Reposado’s very good.
In general, Reposado tequilas are a good middle ground for margarita-making and sipping. They’re a little more expensive than the silvers, but they add a lot of extra flavor if you’re mixing, and they’re not quite as complex as an Anejo, which might be a little much (in taste and expense) for a casual sipper.