In order to improve your language skills, your conversation with language partners should be as diverse as possible. This way you can acquire a broad vocabulary and learn all the different sentence structures in a language. Below you can find some suggestions for conversation topics that would guide you to achieve this.
After the initial introductions, ask your conversation partner why they are learning your native language, for how long and how they have been learning it, how often and in what situations they speak it and to describe their first speaking encounter with a native speaker. Ask them in which area of the city they live and if they like it. Now that you have broken the ice, you can both talk about what you do and how you enjoy your spare time.
An interesting aspect of getting to know somebody from another country, it's to learn about their culture. One way to do this is to compare the differences between the two countries, such as pace of life, type of jobs, quality of life, cuisine, drinking habits, how people spend their spare time, ethnic makeup, social structure, climate, topography, educational system, ... If you are talking to a foreigner, you can ask them how their lifestyle is changing as a result of the new environment and how they feel about it.
Keen language learners are often also keen travelers. Ask your conversation partner if they like traveling, what are the most interesting places they have been to, what they think are the best holiday destinations, what are their country's most popular tourist attractions, if they prefer traveling on their own or taking a package tour, what they miss most when they are away from home, if they are planning to travel shortly. Ask them if they have ever met anyone interesting while on a journey or if they have ever come across any unusual food or drink.
One way to practice grammar is to talk about hypothetical situations. While this is not a topic in itself, you can always ask hypothetical questions in most topics of conversation. Not only would this spice up your conversation, but it would also be a good way to practice some difficult verb tenses. Take, for example, the topics above. If you and your language partner are talking about your jobs, you can ask: "If you had the choice of doing any job, what would it be?" If you are talking about your language partner country's economical and political problems, you can ask: "If you were the president, what would you do first?" If the topic of conversation is traveling, you can ask: "If you had to choose a country to live in for the rest of your life, which one would you choose?" The possibilities are limited only by your imagination!
This is without a doubt a much loved topic and you should make the most of it. Ask your conversation partner what their favorite group / singer / radio station / type of music are. Ask them when and how often they listen to music, if they often go to live concerts, if certain music brings memories to their mind, if there is any kind of music they can't stand, if they play any musical instruments, if they can sing, if they have ever sung karaoke, if they know the lyrics of a song in their practicing language. If you are talking to a foreigner you can ask who the most popular singers in their country are and if they can now listen to them on the radio.
One way to get a good command of a language is being able to express your opinion about any topic. As with hypothetical questions, expressing your opinion will enrich and enliven the conversation, however do not be a know-it-all, but respect the opinion of your conversation partner and try to keep an open mind if you disagree with them. You can ask an opinion on nearly everything. Take, for example, music. You can ask your conversation partner how their opinion of good music has changed over their lifetime, if they consider CDs to be expensive or what they think about downloading free MP3s from the internet. Be extra careful when talking about religion and politics, as people tend to get quite passionate about them.
Another way to start an interesting topic, is to ask the "Have you ever ...?" question. Here are some examples:
Ordering food, describing a person, shopping, clothes and fashion, money, celebrities, gossip, food & eating, meeting people, sports, marriage, children, education, books, computers, science and technology, annoying things.