Carmen Rhor, Peru
Regardless the kind of institution your are working for, or the kind of evaluation you are assessing, in my humble opinion I think that as a teacher you take the following tips for observing a colleague.

Sit among students and discreetly take notes, just try to be part of the class participants. The presence of an observer is always intimidating no matter how experienced you are, so don't make it even more difficult for the observed teacher. In addition, make your visit short (15-20 minutes) would be good enough. Make a short, concise but accurate report ASAP, and have a short talk to him/her in order to give feedback. Give recommendations, hand in handouts that might help him/her improve her/his lessons. Be a facilitator, be a model of a good teacher yourself.

These are just a few ideas I have just gathered in a fast way. Indeed, I am on my way to observe one teacher myself.

Ursula Huancas, Peru
It's very difficult to help you unless you have the objective for assessment very clear.

Besides the other recommendations don't forget if that teacher can also include in his/her lesson plan some moral values, that is to say, if he/she can use real examples from daily life to makes them understand tolerance, respect, etc.

I really hope this can help you a little bit.

Abdelaziz Dqaqi, Morocco
Hema, I think that these elements are very important while observing an ESL teacher in action:
1-Does s/he arrive on time.
2-Is s/he well prepared.
3-Does s/he greet the learners.
4-Does s/he know the students' names.
5-Good classroom management.
6-Good blackboard management.
7-Does s/he use visual aids.
8-Does he use l1.
9-Does s/he correct errors explicitly.
10-Does s/he use technology: laptop etc.
11-teacher's talking time.
12-Is s/he consistent: does s/he keep his/her promises.
13-Is s/he fair with the students.
14-Does s/he check understanding.
15-Does s/he resort to group work.
16-Does s/he integrate the 4 skills.
17-Does s/he use games.
18-Does create an anxiety-free atmosphere.
I hope you will find these ideas useful. Good luck

Viviana Kay, Argentina
I think it is also very important to greet students and make some relevant comments related to their past activities or any special event they may have had so as to set a friendly atmosphere before starting with the class itself. It is also very important to listen to what students tell you and show real interest in their topics.

Piret, Estonia
There are some more aspects to teacher observation. First, you must have a preliminary session clearly stating why and what you'll be observing. Then, in the classroom your observation is focussed on 2-3 (or just 1) aspect, e.g. the ratio of active participation. After the lesson, again a discussion which must include constructive criticism.Furthermore, it is very useful to tape the lesson, either on an audio or video tape. It is very useful that the teacher see him/her in action from aside. A discussion might follow with colleague(s).

Praharsha, India
As far as assessing a teacher is concerned, you need to give him at least 2 sessions of 40 mins for proper observation in which you observe the following:
1.Speech-Its audibility and clarity
2.Teaching method-If it allows innovativeness or not
3.Whiteboard skills-How appropriately is he using it
4.Body language-I must say very few people pay attention to this aspect in teaching.
5.Planning-Does he prepare for the class or not
6.Teacher student interaction-If the class one sided then it really turns off students at any level

Jandira Xavier Moreira, Brazil
I suggest you to try some of the key features below:

Teacher planning
Even If the lesson is from a textbook it must be adapted to the needs of your students.

1. Teacher follows the plan: a( ) strictly b( ) flexibly c( ) limited
2. As the teacher knows he/she is observed, does he/she provide a copy?
3. Is the plan clear? Does it present similar points as:

• Aim / Objective
• Content
• Material
• Steps of development / sequence
• Expected time (timing)
• Activities / Tasks
• Evaluation

Teacher- students
Does the teacher

1. Remind students what they've learned previously?
2. Preview new lesson?
3. Stimulate for new activities?

Does the teacher

1. Have class' attention?
2. Get feedback from students?
3. Stimulate group work?
4. Provide adequate level lesson, age and students reality?
5. Have good time control?
6. Offer help?

Heath Jeffrey, China
Hema, it is difficult to give you a proper reply because it is not clear why you are assessing the teacher. Is he applying for a job with your company? Are you doing an employee review? Are you gathering research for the government? Are you on a teacher-training course? If you were able to provide more specifics in your question, we'd be able to provide better answers.
That said, I will give a few suggestions to begin with. These suggestions are based on the typical things teachers are introduced to on initial teacher training courses, and are therefore quite common things to observe:

• Teacher talking time: Does he/she talk too much, giving students few chances to practice? Is the teacher talk relevant, or is it just rambling or time-wasting? And in some cases, does the teacher talk enough? Does he/she give Ss a chance to hear useful language? Does he/she challenge the learners?

• Classroom management: Does the teacher use the whiteboard effectively? Is the whiteboard clear, easy to read? Does he/she use a mixture of groupwork, pairwork, working alone and whole class work? And are those groupings suitable to the activity? Do the seating arrangements promote language learning?

• Staging: Do the different stages and activities throughout the lesson flow together? Are they connected and relevant to each other? Is there variety in pace Vocabulary instruction: Does the teacher provide students with appropriate, new, challenging, immediately useful language? Does the teacher provide enough single words, and polywords, and expressions? When explaining words does the teacher use simple enough explanations? Does he/she use mime and pictures when appropriate?

• Rapport: Is the teacher polite and friendly? Do the students respect the teacher and trust his/her ability? Does the teacher get along well with the students? Does the teacher make students feel interested and motivated to learn?

This is really a very small selection, and it will be impossible for you to observe all of these things in detail at the one time. If looking at hiring a new employee, I'd suggest taking the most general of these points and looking at each one briefly. If providing advice, or doing some kind of research you should probably choose just one of these points, and look at it in detail.

Engy
Ok , this is very simple. You will have to attend class with this teacher.

1- Is he usually on time for his class?
2- Does he prepare his materials before coming to class?
3- Does he start his class by stating the aim and objective of the learning session?
4- How does he address his students? Their first name, nicknames, or he does not remember their names?
5- Does he welcome them and make them feel at pace?
6- Are they bored during class, if students get bored then there is a miscommunication between both.
7- Does he give a positive feed back to their students after they finish a task?
8- Does he provide a detailed summary to the student at the end of his session?
9- Ask students to write a review about their teacher, how do they evaluate him?
10- What are the results of the evaluation sheets he gives to students?

Steve Hirschhorn, UK
Some of the respondents to your question have pointed out that before observing (or responding to your question) it's essential to know the rationale - I agree 100%! In addition however, observation seems to have become a tool for teacher assessment rather than a collaborative support device. In part this is a historically accepted phenomenon but there is reason to challenge it. Briefly, no-one can tell you what constitutes ‘good' teaching, we have scant evidence indeed for what actually ‘works' in the classroom, instead we are pushed along by unquestioned notions of 'how to do it' which are often only anecdotally supported.

The best kind of observation in my view is that which is welcomed by the teacher, offers support for future development for both teacher and observer, takes account of the teacher, students and their context and is not a tool of assessment. I think that the relationship between observer and observee should be of equals examining an interesting and challenging interaction together, exchanging views and opinions – not the all-knowing Senior and his/her subordinate.