Low cost plane or sleeping car from Ankara to either Adana or Gaziantep.
From Adana, take a bus to Aleppo, may be with a change to another bus or minibus at Antakya.
From Antep, take a minibus to Killis, a taxi to the border, another taxi up to the first village in Syria and then a minibus.
There are comfortable trains and buses between Aleppo and Damascus.
May be you want to visit Syria too. In this case, you will stop at Aleppo, Hama and Homs as bases of tours in the Hinterland.
Here is a summary of all the answers given in the last months concerning the Antep - Aleppo border crossing:
"I did the crossing back in 2005
I remember having taken a minibus(dolmus) from Gazientep Otogar station to the borders with a stop trough killis.
At the borders we crossed the nomensland walking. I takes around an hour and half to go through syrian custums (very unergonised)
Once in syria i took a kind of pickuptruck to the closest village, the guy wanted to charge me 600 liras but i ended up bargaining down to 100.
From this village (i forgot the name) you can take a dolmus to Aleppo for 25 liras
Cheers
I have found the following in this forum:
Gaziantep - Aleppo
http.haleptaksi.com, Tel. Gaziantep 009 - 0.533 342 92 93 Aleppo 00963 - 93 56 82 78 offers taxi service between Gaziantep and Aleppo.
You may also organise a Syrian taxi: Mohamed Abu Jabr, mail: syriatravel@gmail.com.
ChristelB Posted: 30 Oct 200710:42pm
Hi, You can easily get a taxi to Turkey in Aleppo (see above).
Hi!
Few weeks ago I made a trip from Gaziantep to Aleppo. According to Lonely Planet there are no direct buses. I took one of frequent minibuses from Gaziantep to Kilis (5 lira) and then in Kilis bus station I as approached by local taxi or tourist company who offered a car with driver to Allepo. Luckily there was one more passanger from minibus who was going to Aleppo. I paid 20 lira for the trip, so I suppose the price for car is 40 lira. But Lonely Planet says you can go by taxi from Gaziantep to Kilis and then hitch to Azaz in Syria where there are buses to Aleppo.
.
so i just returned from syria. took a commuter busto killis from antep (5 turkýsh lira), then a taxi to the border (10 TL), walked across the border, received a visa at the syrian border (56 US for Canadians, 16 US for americans), then took a taxi to hijaz (150 syrian lira), and finally a bus to aleppo (20 syrian lira). you could also take a taxi to aleppo from the border for about 600 syrian lira.. that is what i paid on my way back.. but beware, if you walk back to the turkish border after dark, you may not find a taxi to take you back to killis to do the reverse trip. the LP book says it is 7 km, i think they meant 7 miles.
just a note, the border guys are great. on your way back, bring them some cool magazines (preferrably arabic, or lots of pictures if not arabic) and it will make your visit more pleasant, especially if had to wait there for an obscene amount of time for your visa."