Try and rock the wheel at a right angle to the axle. If no play is present you're good to go.
Lastly, if you've ever looked at a spoke wheel and wondered how those spindly little wires on the bottom could support an entire motorcycle, let alone the combined weight of the bike, rider(s) and luggage, the answer is they can't. Spokes work very well in tension but have very little compressive strength. Essentially, the motorcycle hangs from the upper spokes while the other spokes simply keep everything aligned and prevent the rim from wandering away. This is key, because once spokes lose tension, the rim and hub quickly fall out of line. Ride a bike with loose spokes for any length of time and chances are good you'll soon be rebuilding the wheel, which is neither cheap nor something a novice should be tackling unless he's got a lot of time and a real interest in becoming a wheelwright.
The Practice
Wire-wheel maintenance involves a few simple tasks and even fewer tools. The wheel needs to be inspected on a periodic basis for physical damage, loose or worn components, alignment problems and, most importantly, spoke tension. So what's periodic? Certainly, I'd give my rims the once-over if I whacked a pothole or big frost heave or maybe ran over the neighbor's kid's bicycle (don't ask), but the only time I really give them a formal inspection is when I do major service or install new tires. So, in this case, I'd say that periodic means every 3000 miles or once a year, unless your owner's manual specifies otherwise. Of course, since the whole job takes maybe 15 minutes to half an hour, you may want to perform it on a more regular basis.
While a decent job of inspecting the wheels can be done with the bike on its kickstand, it'll be far easier if the bike is upright, with both wheels off the ground. If your bike doesn't have a centerstand (and whose does these days?), use a lift or whatever it takes to get the bike into position.
A tie-wrap makes an impromptu, yet perfect, wheel truing device.
A cracked rim is rare but not unheard of, so I like to start by inspecting that hoop for fractures. Most are small, hairline fissures that radiate outward from the spoke holes, and in most cases will run from one hole to another. If any are found, the rim will need replacement, but like I said, cracks are rare. Hub cracks are even less common, but it never hurts to give everything a look, just in case you're one of the lucky ones.
Modern wheel bearings are paragons of reliability and generally don't cause any problems unless they've been severely abused, typically by being hosed down with a high-pressure washer or steam cleaner (which tends to wash the grease out of them), or just by a lot of mileage. In any case, a wheel bearing will normally start to "rumble" or whine before it reaches its expiration date, so the easiest check is to just spin the wheel and listen; if it doesn't turn smoothly or there are weird noises coming from the hub center, a further look is warranted.
A bearing can sometimes develop excess freeplay, which will affect handling for the worse and eventually cause bearing failure. To check freeplay, raise the wheel slightly off the ground and grasp it at opposite points (12 and 6 o'clock work as well as any). Try to move the wheel back and forth, 90 degrees to the axle. In some cases, slight movement may be normal or at least acceptable (your service manual will have the details), but as a rule, any kind of shift indicates the bearings need adjustment or replacement.
From the top: spoke torque wrench with interchangeable heads, universal spoke wrenches and standard spoke wrenches.
The last type of wheel check is for true or runout (jargon for out-of-round). There are two types of runout: axial, which is a side-to-side wobble, and radial, which is an up-and-down hop. Both checks can be performed well enough by eye, at least initially, as all you're going to do is give the wheel a spin and watch it rotate. If the wheel appears to be rotating true, chances are pretty good everything's fine. Since no wheel is 100 percent perfect, manufacturers typically allow between 1 and 3mm of runout in either direction.
If there's any doubt, fix a pointer to the frame or fork (a tie-wrap will do fine), and allow it to just kiss the rim at the closest point. For axial runout, position the pointer to the side of the rim. To measure radial runout, select a point on the rim's inner or outer edge. Slowly rotate the rim until the gap between the pointer and the rim is at its greatest. If the dimension exceeds the manufacturer's recommendation, the wheel will need to be trued.