Without knowing what kind of motorcycle it is, and if it's new or used, it is hard to determine.
The good news is that it isn't necessarily a bad clutch. The rest of the news is that you're going to have to find out what is causing it.
In order of easiest to hardest:
1) Grease the clutch lever itself.
2) Lubricate the clutch cable (if cable driven).
3) Remove the clutch slave cylinder (near your left foot), then pull out and clean, and re-grease the silver push-rod. [This FREQUENTLY fixes hard-to-shift problems.]
4) Possible clutch problems.
If it's not #1, it's most likely #3. Removing the slave cylinder and cleaning the push rod is about a 30 minute task.
Hint for hydraulic clutches: Once you have the slave cylinder removed, do -not- apply the brake. If you do fluid will leak out of places you don't want and you will have to fully bleed the clutch system.