Essentially the simplest way to put it is, make it a place you'd want to buy and/or live in. The nicer things look the more value you will add - but this doesn't mean that you will need to do a major renovation. Small changes can also make a difference in the value. Also, if you spend more money, that doesn't necessarily mean that the value added is proportional to the amount of money you spent. Let's get into it:

Paint Job
This is one of the best and easiest ways to add value to your property. Painting will give the place a nice bright look but choose a nice colour. Keep it simple and select colours that are neutral and the majority of people will like. Painting will also get rid of any smell that has accumulated over the years in the property. When cooking, the smell tends to stick in the walls (especially heavy spices) so a new paint job can also get rid of any smell lingering.

Outdoor Living Space
If your property has a decent size backyard, it will be worth adding an alfresco or upgrading your existing one. You may want to add some electrical blinds for shade, or firepits and add some plants for character. You should also consider a nice landscaping job which makes the backyard a nicer place to be and entertain guests. If you're selling your property, these things help in fetching a higher price.

Upgrade Kitchen
The kitchen is considered the heart of every home - it's a high traffic area and is very likely used daily. Consider giving it a makeover, either with a cosmetic lift or even completely modernise the design. Minor upgrades such cleaning cupboards and cabinetry, swapping handles or changing the splashback makes the kitchen seem nicer. If you've got the budget consider changing the benchtop, sinks or even the entire layout of the kitchen.

Upgrade Bathroom
Another area which obviously has high traffic - upgrading your bathroom can make a big difference. You can consider replacing the shower screens or curtains and get rid of the mould in the bathroom. Replace cabinetry, swap out the handles and even consider a flooring upgrade, replacing sinks or toilets if you've got the budget.

Flooring Upgrade
Another easy way to add value to your property is to upgrade the flooring. If you have carpeted areas, consider changing these to floor boards as carpets tend to look very bad typically.

Upgrade Entrance
Street appeal increases desirability. If you're selling the property and you have an inviting entrance, it is likely to increase the property value. The whole "Keeping up with the Joneses' syndrome is strong with this one and many people want the best looking property on the street. Consider a decent entrance with some landscaping, replacing the main door or adding a porch.

Build a Granny Flat
This is probably the most expensive option on this list, but basically a guaranteed way of adding value to your property. If you've got a decent size backyard, adding a granny flat will attract more buyers. If you want to continue owning a property, you can also rent the granny flat out for more income!