What should I be aware of if I would like to start training Aikido? I used to train as teenager in small dojo. I picked up few tricks but I never got the essence of Aikido. Is there something you would recommend I research or be aware of before I signup with local dojo?
The best indicators I ever found were:
With those you should not err too far. Note that those are not only applicable to Aikido but especially the injury and qualifications ones are very applicable.
Aikido can be hard on the wrist, knees and ankles. Break falls can be hard on your neck and back. Thus it is important to know your limit and pay attention to instructions.
Note that qualifications includes both proficiency at Aikido (which can be hard to judge) as well as teaching qualifications and insurance.
As for styles, pick the right dojo. Do not worry about the style as in the end, it is all Aikido.
It doesn't matter what they say about the school. It matters what they do.
I believe, the answer to the question lies in measuring the schools ability to help you find what you are looking for. So go to the school and look for people who you can relate to.
If you can see people that you have something in common with and you can see people making progress along a path of change that would motivate you then this is a good school for you.
For example I heard once about this Aikido dojo that had a very impressive student body, they looked great. For their warm up drills they did forward hand springs. It turns out they were from a University and had been recruited from the gymnastics team.
What we are looking for is a place where we can make progress on our own path. If you can see in the school the kind of change you are looking to make that school will probably work for you.
I wrote something a few years ago that is still fairly relevant. The thing is - how do you choose a school, and that is not specific to aikido. I hope this helps -- let me know if this brings up any questions in your mind.
The basic point is: make sure the teacher is personable and not just trying to sell you on a subscription. Pay attention to the students. How do the beginners look? How do the intermediate students look? The intermediate students should look like they have an idea what they're doing, and should look worse than the advanced students.
Finally - as a student, once you have chosen a school, you have a responsibility to shut up, listen and learn.
It depends on what result you expect from studying martial arts, but in many cases it will be useful to look at the students there.
In most martial arts with sparring, students who are taught by a good trainer will win in competition. I suggest instructors which have such students are better than those who have not.
In most cases in Aikido there is no such scale, but you can ask about certifications (both student and instructor).
Anyway, there must be some external verification of instructor quality available.
Try to consider the dojo as a whole. Beside avoiding scams and cult staff you should look at this:
Avoid dojos where senior students regularly give explanation to novices. That's a break of etiquette and should be a seldom exception.