Seyidina Ali (Radhiallaahu Anhu) mentioned that good friend and neighbors have the following qualities:
1) Forgive the shortcomings of the friend
2) Show pity to the friend's difficulties
3) Conceal his shortcomings
4) Overlook his excuses
5) Accept his forgiveness
6) Stop the backbiting spoken of the friend
7) Always be with the friend
Protect the friendship
9) Fulfil the needs of the friend
10) Visit him when he is sick
11) When he dies, be present at his Janaaza
12) When invited, accept his invitation
13) If he gives a gift, accept it
14) If he does good, then reciprocate accordingly
15) When the friend offers a bounty, then thank him
16) When he needs help then assist him
17) Preserve the honour and respect of your friend and his
house
18) Fulfil his needs that accord with Shariáh
19) Accept his intercession if it is according to Shariáh
20) Do not make him despondent in his requests
21) Reply to the friend's sneeze by saying "Yarhmukallaahu" if he said 'Alhamdulillah'
22) If anything is lost of the friend, then assist him to look
for it
23) Reply to his Salaam
24) Support and praise his good works
25) If one has taken an oath to fulfil something, assist him in accomplishing the oath
26) Assist your friend at all times whether he is an oppressor or oppressed. Assisting him if he is an oppressor is to stop him from oppression.
27) Also communicate with him and do not create
animosity.
28) Don't disgrace a friend don't swear a friend. Source: http://islamicfrat.com/index.php/post/104-qualities-of-a-true-friend