To decide which guitar strings to use, I usually look past brand. More important are the gauges, and materials used to make the strings.
This refers to what the strings are wrapped with. My favorite is pure nickel, as that is the material that was used back in the 60s and 70s. It has a much warmer, richer tone. If you want a brighter, more modern sound, then stainless steel might be the right option for you.
Most brands have string gauges that range from light to heavy, but they are all standard gauges usually. For example, if you are trying to get the Jimi Hendrix Tone, you would ideally want 10-38 pure nickel, which is not easy to find these days. Generally light strings will work for that sound and make bending much easier. Though if you want a heavier sound, like Stevie Ray Vaughan for example, then you want to go heavy, about 13 on the highest string. While it does make bending more difficult, it will make your solos much fatter.
Good String Brands
If you go to your local music shop, they will usually only carry quality strings. So don’t be set on buying the most expensive set. First follow the guidelines above, and then pick a brand. I’ve used Ernie Ball, D’addario, and Fender, which have all been quite nice. I continue to use Ernie Ball as they always have the pure nickel option that I like.
Use your Ears
The best thing to do in the beginning is to try different brands, gauges, and string materials and see which sounds the best to your ears. In the end, its all subjective. After some trial and error, you’ll find the right strings for you and your tone.