How can I make french press coffee taste less acidic? Is there a trick to making coffee, particularly french press, taste less acidic?
Without any more specific information about the coffee you use and what recipe you use for the french press, we won't be able to give you a specific answer with a solution to your problem. However too acidic probably means that your coffee is underextracted. That means the water hasn't had enough time or wasn't hot enough to extract the flavor compounds you want out of the ground coffee.

There are a few variables that will influence extraction with french press. I already mentioned time and heat. A recipe that I have used with very good results is 6g coffee per 100ml of water, ground to the size of coarse salt with a steep time of 4min. At first you only add a little water (just off the boil), twice to three times the weight of coffee grounds and let sit for 1min. Then give it a stir (there will be grounds on the top forming a crust), add the rest of the water and wait until 4min. Plunge and immediately transfer your coffee to a preheated vessel, either your mugs or a jug. Important here is that you don't let the coffee sit as it will continue to extract and taste bitter after a few minutes.

This should give you an even, full bodied extraction. If you feel like it's still too acidic, you could vary the variables involved. If you grind slightly finer the extraction will be higher. Same thing if you increase the brew time a bit. I suggest you just play around and keep in mind that these variables are not independent of each other. Finer grind means faster extraction for example. With a basic understanding of how extraction works you should get the hang of it quickly.

If the coffee still tastes too acidic although you have tried all suggestions check if the roast is too light, since light roasts tend to have more acidity. Also the origin of your coffee is a factor, african coffees (there are many different regions and processing methods so this is a big generalization) tend to be more acidic, while sumatran coffees are considered the least acidic. Central and South American coffees will often have acidity levels in the middle range.
It might also be sour because the coffee is stale (around 4 weeks after roasting for whole beans, much much much faster for preground) or it might just be shitty coffee.

This is a good little intro in the world of extraction (or rather which tastes are associated with different levels of extraction):
Coffee Extraction and How to Taste It.

This is a very nice little graphic with explanations that helps identifying which extraction problem you have and how to solve it:
The Coffee Compass.

Cheers and enjoy a nice cup of coffee.