Best Tip/Trick: Practice. You don't always have to strum or pick, you can just fret notes on the neck. It will take a while (depends on the person) to develop your fingertips.

Worst Tip/Trick: Summer of '69. Do NOT play until your fingers bleed. Scar tissue isn't the same as calluses.

If you develop a blister, let it pop, then keep practicing. Ther's no need to reshape the skin to remove the small divot. Practicing will usually wear your fingertip back to a normal shape.

Take it slowly at first with short practice sessions. You'll be able to increase your session length as your fingers toughen up. If you do have the desire to practice, but your fingers hurt a bit, take some time to watch some videos/read about the other important aspects of being a guitarist:

Posture. Just sit with your guitar in your playing position and work on staying upright. If you notice that you're getting some wrist pain after playing (a little is natural since you're holding your hand at an odd angle), work on finding a neck angle that works for you. (I tend to play with the neck "crossing" about mid-bicep since it's comfortable for me.)

Guitar Care

String Changing

Set-Up and Intonation: It's cheaper to do it yourself, since most places will charge you a price equal to a couple packages of strings. (I'd rather have spare strings than spend money on something that's easy to learn.)

Music Theory (it's never too soon to start)

Your Idol's Biography and other guitarists you admire too. Never know what you'll find out that may help your development.

Take a Walk! Get some exercise! Listen to music while doing so and work on your internal rhythm. I'll go for a walk while listening to music, making sure that one of my feet (always the same for the song playing) hits the ground on the first beat of each bar/measure. Then, depending on the tempo, it will usually hit the ground again on the third beat for slow songs (the other foot will hit on the third beat for really fast songs).

Eat and Rest.

Optional: Learn some about soldering parts if you're an electic guitarist. It'll help with repair and upgrades.

Hope this is helpful and have fun.

If you do experience pain while playing, stop and identify the cause of the pain. Then figure a way to not have it happen again. Some discomfort is to be expected, you're doing things with your fingers/hands that you probably haven't done before. Asking your fingers to spread and press down at the same time can cause some discomfort, but it goes away with practice. There are also some stretches that you can do help limber up (fingers, wrist, shoulders, neck are all helpful).