I'm in a deathcore band or hardcore what ever you want to call it and iikmm making up riffs but my fingers get tired after doing these certain trills after a while and they start to get sloppy, i want to know how to practice for these trills so my pinky becomes more stronger.

these kinds
the two intro riffs here:

and this is the song:
Deathcore Head
Death Tech Metal Head
Shred Head
Jazz Head

Quote by NGD1313
Well I don't know about solos but how about that Smoke on the Water riff. It's like...impossible.

it'll be a strectch at first, but you'll get used to it.
Quote by pedromiles101
you're not gonna want to take a dump in a gross, off-colored, vintage toilet. you want something that is white and pearly; something that shines. something that you can put your cheeks against and say, "f*** yeah"
A good (and somewhat painful) exercise is a 6 minute drill. hammer-on and pull-off continuously and evenly for 1 minute between your first and second finger on the first and second fret. Then do that for the first and third finger on frets 1 and 2, then first and fourth, then second and third, second and fourth, and finally third and fourth. Usually you do it without stopping between sections. You might want to just start off with just 15-30 second intervals at first though. Eventually those kinds of licks will be a piece of cake.
those aren't trills, those are just regular hammer on/pull offs. a trill is done by hammering and pulling off between two notes as fast as you can. but the best way to learn it is to just simply do it. practice it enough and your pinkie will get used to it. Bring me the horizon has an instrumental song called slow dance. the main riff is a run of trills. thats the song i play to brush up on it. there are tabs for it here on UG. i like to trill stuff in thirds kinda like harmonizing by yourself, thats basically what that song does in the main riff. good luck man
I would try taking the main pattern at the beggining before he ascends and looping it without the bassline - just 8h12p8h12-7h10p7h10 - for approximately a minute at a time (or less at first if you get too sloppy by the end of the minute). Don't go too fast - this isn't the real lick, it's an exercise to help you play the real lick, so you don't need to reach song speed - keep it slow-medium tempo and focus on getting it even, and getting the technique as effortless as possible.