How much should we be lifting?
There are a number of ways to think about this question. You need to consider what the purpose of the session is, whether it's general strength training, maximal strength training, training for strength endurance or power. Whichever of these you decide on there are then 2 ways of looking at it.
You've decided you're going to do 3 sets of 10 reps, thats fine, it's a good starting point and for general strength training it works.
What weight you decide to lift is determined by your 1 rep max (1RM) this being the absolute most you can lift once. Of course you 1RM deadlift isn't your 1RM for everything, so if you're doing front squats you need to work it out for that and likewise for bench press or any other lift you do.
There is another way to consider how much you should be lifting, and that is simply that your last lift of your last set should be that last one you can do, maybe you have 1 or 2 more reps in you but no more. This is called overload and that how you get stronger.
How to calculate your 1RM
It's not easy to work out your 1RM by doing one lift, you actually end up doing about 10 or maybe more, and so you need a decent recovery between every lift so that you are lifting every lift fresh.
There are ways to calculate your 1RM based on doing 3, 5, or even 10 reps. This is probably easier and safer too if you're not an experienced lifter, especially when doing front or back squats or bench presses for example. for safety reasons get someone to spot you when lifting at you limit, and make sure they know how to spot someone correctly.
This table (taken from Jovanovic, 2014) shows how lifting a number of reps would equate to being a percentage of your 1RM. Then using the 1RM calculator here you can now find your 1RM based on what you actually lifted and how many times.
Considerations for doing a 1RM test
Spotters are essential
Warm up at around 50% of predicted 1RM
Add more weight based on ease of previous lifts
Should be able to reach your target attempts of 3, 5 or 10 reps within 3-4 sets. lifting more than this will make you fatigued and your 1RM calculation won't be accurate
Be strict with technique, if technique goes at this weight then you won't be able to lift the 1RM therefore being strict at lighter weights ensures you will be able to lift close to your 1RM when you need to.