The Moorish Alhambra fortress and garden complex is the highlight of Granada, but tickets are limited and the line to get them can be ridiculous - you can expect to wait for two or three hours at peak times. Guided tours, on the other hand, guarantee entry and eliminate standing in line. Alhambra guided tours can be taken as part of a larger tour of Andalusia or independently. See below for the best tours of the Alhambra.
A guided tour of the Alhambra fortress and gardens. The cheapest option, only taking a few hours out of your schedule. Your guide will pick you up from your Granada hotel for your tour. If you are not actually staying in Granada, other meeting points can be arranged.
Wind down after your guided tour of the Alhambra with a visit to Granada's Arab baths.
If booking visits to Arab baths on your own, you'll usually need an appointment during high season. This organized tour takes the hassle out of having to do this once you get to Granada.
This tour departs (very) early from your hotel, taking you to Granada for a guided tour of the Alhambra before giving you some free time to explore the city of Granada by yourself.
Similar to the above trip, but with departures from Seville. Due to the greater distance between Seville and Granada, you have less free time on this tour than on the above tour.
The same as above, but condensing your time in Granada into a single day. Granada merits more than a single day, so I'd recommend the above tour over this one, but if you're short of time, this is a nice taster (you could always come back!) and offers the same advantages as the previous tour.
Toledo, Ronda and the Alhambra are three of the most difficult sights to visit independently in Spain (see Organized Tours vs Independent Travel
for why). On this tour, you see all three.
Starting in Madrid, you visit Cordoba on day one. Day two takes in Seville, day three is spent in Ronda and the Costa del Sol, day four in Granada and day five takes you to back to Madrid via Toledo.
Though this tour crams a lot into five days, it is a hassle-free way of seeing some of Spain's absolute gems and conveniently leaves you back where you started in Madrid.
See also a similar Tour Departing from Barcelona instead.