Isopropyl alcohol from your pharmacist or on-line retailer (or from tax avoiders like Amazon if you are desperate) for the tape heads and capstan i.e. metal parts, only.
If you are serious about the long term health of a deck use a proprietary rubber cleaner for the pinch roller (alcohol will cause the rubber to dehydrate and crack eventually).
Use a lightly soaked cotton bud to apply the above items.
Light pressure is enough when cleaning the tape heads. You can use a tiny bit more on the capstan & pinch roller. Keep washing and alternately drying the pinch roller until the cotton bud comes up clean and you are done. :)
Note : to activate the capstan and pinch roller, for ease of cleaning, switch the machine into "play" mode then press the pause button. This will separate the roller from the capstan and allow you to clean the capstan. After this you can re-engage play and clean the rubber with a different compound. Take care to sympathetically position the cotton bud on the rubber so that it doesn't get dragged into the capstan i.e. place the cotton bud on the side that's moving away from the capstan ;^)
If you are a perfectionist you can revisit the capstan afterwards and clean and polish it to remove residue.
Do these cleaning operations frequently (playing hours in single figures) or if you feel the machine is getting "sticky".
If the tape stops do not restart! Eject and carefully remove the cassette then rewind the slack by hand. be gentle and don't force it. The tape will virtually spring free by itself.
Final note : watch out for loose strands of cotton wrapping themselves around the capstan during cleaning. Be careful to avoid the sometimes greasy base of the capstan with the cotton bud and clean it from the bottom upwards, all the way up to the top, to remove those strands.
Leave the machine for a short time to dry and you can start enjoying those tapes.
All the best,