My b/g twins are in 5th grade this year, and my son is the one who used to hate homework. I've learned my #1 offensive to tackle the work is to first lay it out, and break it into smaller tasks. He tends to get overwhelmed easily so seeing it in smaller pieces makes it much more managable for him.
I agree - if it's optional work, don't stress about it; yet don't throw it away either. Keep the sheets in a binder - you'll be glad to have them to work with later.
Right now, it's more about the routine of having homework. Pre-K seems a bit early, but you can use this as an opportunity to introduce the "10 minutes of review" after you pick him up from school. Give him as many choices as possible, "Do you want to open your backpack first, or hang up your coat?" type options "Should we put away your shoes first or pick out a snack?" -except for the time and location of this meeting. When you get home, go to a designated place within the house (for us, we use our dining room as a central place for homework) and casually say to him, "How was your day today?" "What kinds of things did Mrs. Smith have you work on?" "Did you play with Mary and Johnny again?", etc... as you are going through whatever he brings home. He needs to know that you're truly interested in him and his work, and will thrive on your attention. Be sure to use words like excited, proud, fantastic, great job, etc as much as possible. Ask questions about the art project, or craft project- have him tell you about how he did it or what it represents.
When you come to the "homework", tell him that you remember working on this as a kid and how much fun it was. Ask if he wants to show you how his teacher does it in his class. If he says no, then say it's OK and you'll just save it for another day.
When/if he shows interest, be sure to give a time limit too - ask if the two of you can spend 3 minutes working on it to see how it's done. Sometimes an entire sheet of expected work is ovewhelming and it can be more effective to say "Let's take 3 minutes to do 5 problems, then we can have a snack" or go and play with the blocks, or whatever he likes to do. A little reward can sometimes be a motivator.
I learned the "time limit" trick early on - it's amazing the difference in response from "Go pick up the toys before dinner" to "Hey- could you spend 5 minutes and pick up what you can before dad gets home for dinner" It's amazing how much can get done with a time limit. It gives the task a difinitive end and feels less daunting. Sometimes it has to be OK that some of the toys are still left out, but even having 90% of them put away is an accomplishment. The rest can be put away in another 5 minute attack before bedtime.
All in all, kids will respond better without stress, frustration and the negativity. Try making it a game - "I bet you can't do 3 problems in 5 minutes" - which gives a definitive goal that's within their reach. This also made potty training a breeze for us because I let them be in control and make some non essential choices.
Sorry, I tend to ramble on a bit! Hope there's some tid-bits that you can use!