My first year of lifting, I think ALL my upper back work was more of a biceps workout than anything else, I know what it's like. Basically, once you learn how to activate the lats on command (via a lat flare style bodybuilding pose), you'll know just how upper back training should feel as you'll realize how to actually pull with your lats vs. using your arms.
I'd suggest learning how to activate the lats properly before doing too much upper back work as if you have too much accidental focus on biceps, you leave them prone to being easier to injure, so you'll want to learn how to activate the proper musculature before long. Not to mention, you'll be shorting yourself on overall upper back progress in your training.
You don't necessarily need to squeeze the shoulder blades together to activate the lats properly for rowing or pull-ups/chins, rather, here's a few ways to visualize how the lats should activate properly -
ALWAYS think "Pull with the elbows!", every single set for any rowing or vertical pulling movements. You should NOT think to actually intentionally use your biceps on pulling movements unless you're struggling to finish a last rep and need a bit of help, otherwise, you need to essentially train upper back as if your arm stops at the elbow. Any direct intentional incorporation of the biceps for pulling will change things in a negative way immediately, so while learning to incorporate the lats, you need to completely remove all thoughts of the biceps being able to assist on such movements. Yes, your biceps will be recruited indirectly to some degree and may be sore, but if you do an upper back workout and your biceps are pumped and aching and your lats barely feel anything, then something's definitely wrong and needing correcting.
There are two machine movements can can be excellent for training on how to better incorporate the lats for other lifts. Those would include the pullover machine (if your gym has one), otherwise, straight arm standing pullovers on a lat pulldown system or cable tower will also work. Video here for how to perform the movement - http://youtu.be/syYu0wxDKtM
The pullover machine will be self-explanatory, but for the straight arm pullover, it's similar to doing a triceps pressdown, except that you keep the arms either totally straight or a fraction away from being locked out 100% straight (just a few degrees of a tiny bend, barely any), and it will then activate the lats for the movement. If you keep the arms from bending through the movement, you'll find that the lats are what will be doing the work during the lift, as your arms will only work as levers on which the weight moves, but won't do anything much to actually move the weight themselves. It might take a few tries and a few sets to get the hang of it, but it will be one of the easier ways to show how it feels to activate the lats. Once you become proficient at how it feels when they come into play, you will know EXACTLY how it should feel on pull-ups and rows as well. You can also try the Cobra lat pulldown as shown here: http://www.t-nation.com/free_online_article/sports_body_training_performance/best_of_back
This site has some good tips on lat activation - http://relativestrengthadvantage.com/how-to-unleash-your-pull-up-work-out-potential-with-lat-activation/
And, I also recommend lat stretching, where you grab a pole or small pillar with both hands at around belly button height, toes are up against pole or close to it, and slowly shoot your hips back behind you to while holding the pole tightly to REALLY stretch the lats out. You can do it with both arms at the same time, or, one at a time as in this clip: http://youtu.be/CCcrajqamds
A good lat stretch will help you recognize the feel of where you should be seeing things activate during your lifts. Eventually, the benchmark to being able to fire your lats properly is that you'll be able to flare them on command, or, at least make them cramp up just by pulling your elbow into your ribcage against an imaginary resistance. Once you can do those things, you'll be set for life on how to get them working on your other lifts!