One of the biggest reasons why you might want to get a recliner is the ability to put up the footrest and relax. However, over time, this can sometimes result in the footrest wearing out or getting broken.
Thankfully, it’s often relatively easy for you to fix everything up.

Supplies

Rag/Disposable Cloth
Spare Parts
Lubricant Oil
Old Newspaper
A standard screwdriver
A Phillips screwdriver
Wood screws
Spare parts (in such case, try to contact a manufacturer first)

Step 1: Get the Chair Into Position

The first thing that you need to do is get the recliner into a position where you can comfortably work on it. To do this, you’ll need to lie the chair on its side, with the weight resting on the armrests. This should allow you to see under the recliner. By doing this, you’ll be able to see how everything is working, making it easier for you to fix any issues you discover.
You can even install the lamp (a regular one from Ikea works just fine - here is a picture of mine) to get a better view.

Step 2: Check the Screws

In many cases, issues like a sagging footrest will be caused by old screws. You’ll be able to find these screws on metal rails, which connect the footrest to the main metal structure. Over time, these can come loose. If this is the case, you might be able to solve the problem by tightening them up. You might also need to remove and replace the screws.

Step 3: Lubricate the Screws

If you’re still experiencing problems, you might want to try to lubricate the screws. To do this you’ll need to loosen up the screws along the pullout mechanism. Then, place plastic sheeting across the cushions. This will ensure that they aren’t damaged during the process. The next step is to apply the lubricant (beeswax as an option, but here are some additional ideas). As you do this, make sure to be generous with your spray, coating all the components evenly.
This might help you with squeaking recliner as well.
When you’re finished, tighten the screws and turn the chair upright again.

Step 4: Adjust the Tension on the Footrest

At this stage, the footrest shouldn’t be sagging. If it’s still drooping, you might want to change the tension on the footrest. This should be a fairly simple procedure to complete. You’ll notice that the footrest mechanism features a set of springs, on each side of the frame. If the footrest is too firm, you will need to move the spring forward by a peg. If it’s sagging, you’ll need to increase the tension, by moving the spring back.

As you do this, you might want to use a specialized tool, like a hook, rather than trying to adjust them with your hands (haven't mentioned them on the list as an essential tool, so that's up to you whether to use it or not).

Step 5: Conclusion

After adjusting the tension, test out the chair, to find whether you’ve solved the problem. It might take a few attempts until you get the right amount of tension on the spring.

Once again, keep in mind that you can always get some spare details for your recliner from a manufacturer (that's why I love LazyBoy, for instance - it's quite easy to find some and to get some help from them).

Now you have a better idea about some of the potential recliner footrest issues you could face and how you’ll be able to solve them. By doing these simple techniques, you’ll be able to make sure that your recliner will keep working for many years to come.