Although we can literally do a ton of things in editing, and fix many in-camera mistakes from the comfort of our computer desk, there are some things we just can't fix in processing, no matter how hard we try! Out of focus images, bad lighting, and clipped highlights are some of the things that we simply can't make right after the fact.
Here's are the five things I believe you should get right in camera every time (and why!)
1) The Light
The first thing you need to do is look to see where the light is coming from and how it is lighting your subject. If your subject doesn't look good to the naked eye, then they are not going to look good in the picture either! Make sure there are no unflattering shadows, and that eyes have plenty of light in them - two things that you cannot really alter in processing (at least not without making your subject look like an alien. Trust me. Been there, done that)
2) No Distractions
Once you have decided where you are going to position yourself and your subject with regard to the light, take a moment to check your background for distractions. Of course there are some things which you can simply clone out later in editing, and this is always an option, but be especially aware of things that you either can't change or that would be extremely difficult to clone away - things "growing" out of our subjects heads, or that merge with your subject, or distracting background items such as signs that would simply be hard to remove in processing. (I have literally spent HOURS trying to remove things that shouldn't be there - such a waste of time!)
3) Sharp Focus
As i said at the beginning, out of focus images cannot really be fixed in processing, so it's super important to get it right in camera! Choose the correct focusing method for what you are photographing - Al Servo / Continuous for moving subjects, and One Shot / Single for still subjects.
4) Check your histogram
The other thing you can't really fix too well is clipped highlights. Highlights are the lightest parts of your image, and "clipping" them means that you have lost detail in that area - that area will simply show up as a blob of white. Although sometimes it's acceptable to clip areas in an image, say in the sky, we definitely don't want white blobs on our subjects! You can check your histogram when shooting, and make sure that there is not a spike at the far right of the histogram. If it does have a spike (where it is climbing up the end of the graph - you can see an example below) then you have clipped your highlights - take the image again, but this time lower the exposure.
5) An Intent
My final recommendation is that you approach each shot with an end goal in mind. What are you looking to capture? Is it a lifestyle / documentary shot for your family albums or a portrait to hang on the wall? What do you want it to look like, feel like? The more you can visualise the end result, the more purposeful your shooting will be! If you are just starting out, this is much, much harder to do since you are not yet aware of how to achieve certain things, so in which case, just try to be purposeful about one or two things at a time - perhaps purposefully try to use a certain type of light, or include a certain compositional element with your images and so on. These are things that can only really be done in camera!
If you really want to get your images looking fantastic, then it all starts with getting the basics right in camera - we cover all of this in my ecourse Auto to Awesome too.
If you would like to have a better idea of what to think about before you press this shutter, I've created this mental photography checklist for you that you can download and print at home. Next time you are taking an image, work your way through the checklist, and pretty soon these "checks" will become second nature (and take far less time to consider!)