All beers aim for a good balance between the sweetness from the malts and the bitterness from the hops. Too sweet and it's cloying, too bitter and it's unpalatable. But this balance usually tips a little to on side or the other. Take a sip and notice how these two basic tastes correspond. Do you like it? Your opinion on this is just as valid as anyone else's.
Some people find that word a bit off-putting, but if you're talking beer then it's hard to avoid. Mouthfeel is separate from flavour. Instead it describes the beer's texture on your tongue. This takes into account the beer's body, that is its thickness and viscosity. Is it thin like water or full like milk? It also includes the amount and character of its carbonation.
What's it like after you've swallowed the beer? Often there's a drying effect on your tongue that, when done right, provides a pleasant encouragement to take another swig. If it's done wrong though and you could be looking at astringency - that excessive, tannic dryness. Think of crunching up grape seeds and the face it makes you pull. What about the aftertaste? How long does it go on, how bitter is it, are there any other flavours that stand out? That, taken all together, is the finish.