In my opinion we have 2 steps here.
The second step: Post processing
I'm starting with the second one. The post processing. It is not that heavy at all.
I am not using lightroom on this example but it is the same for diferent aplications. Play with the levels.
1) I aumented the gamma (which is a very specific kind of curve) to arround 2-2.3. (probably in my example it is a little overdone)
Adjust the black level accordingly.
2) Crop the white point. This will pop an extra brightness but also will saturate your photo.
3) You can saturate a bit more your photo. (I did not saturate them in this cases, because I am showing the diference on the histogram when alpplying the steps 1 and 2)
And the first step
Take a good picture from start!
In this example the first photo has a nice diffused light, and in the second one you can see that they used a hard flash that projects some bad shadows. The bright look can be achived, but a pleasent diffused light makes all the diference.
Some tips on taking the pictures
Take advantage of the existing ambient light when possible. Big windows specially.
Bounce your flashes on the white celling, or walls. Note that I mentioned flashes. For a studio photo (or on location one) you normally need several fhashes depending on the kind of photo you need, close ups or wide shoots.
Iluminate your subjects, but also your backgrounds. Depending on the situation this can be difficult, because sometimes on a wide background you can see hotspots everywere. This is why you need to take advantage of ambient light as much as you can.
Use a wide aperture lens. This photos normally have a shallow DOF, because the nice bokeh, but also because... they are using some nice ambient light. If you are using flashes this helps because you can place your flashes further away, and make a more uniform light.