They don't sound it, but ports are important to consider. For example, the Dell XPS 13, whilst an awesome laptop only ships with a Thunderbolt 3 and USB-C ports. So if you lose your laptop charger please consider how to replace it in advance!
If you need a USC-A or you like losing chargers, bear your ports in mind before you spend a lot of money.
2. Power
Too much can be pricey, too little can be fatal.
Take a Chromebook as an example, they are light, agile and hardwearing. You can easily slip them in your bag whilst on your way to university. They have plenty of power if you're doing emails, crunching some numbers or casually browsing. Not to mention they are dam cheap! However, if you're a photoshop guru or like your gaming, these machines will likely not pack enough punch. Especially if you need bespoke and powerful graphics card - this just won't be possible.
3. Price
It doesn't have to just be a MacBook for you to blow a heck of a lot of money on it! The Dell XPS is pricey, so is the Alienware range or the Lenovo IdeaPad. If you're paying for a tonne of cool stuff you're unlikely to use, are you not just wasting money? Probably!
For example, basic games rarely require a full gaming rig costing £2k. Or if you're paying £3k for heaps of TB in storage consider whether you can use the Cloud and save on costs.
4. Practice
Would you buy a house without looking at it? (Maybe nowadays) Would you buy a car without testing it? (Perhaps). Most people try both before they buy, so why wouldn't you with a laptop? Nothing wrong with visiting a retail outlet and requesting this. Most major retailers allow you to do so in advance.
Things to check: the screen, the keyboard, interface, the mouse, the speed of processing, the weight, the width and the potential durability.
If you don't get chance to test it - consider brands like Lenovo who will offer free returns.