Machine learning models are built by following a systematic approach and involves several steps. Here are the general steps involved in building machine learning models:

1. Define the problem: Clearly specify the problem you are trying to solve. This step involves understanding the problem domain, gathering requirements, and determining the objectives.

2. Data collection and preprocessing: Collect the relevant data required for training the model. This could involve sourcing data from various sources like databases, APIs, or web scraping. Once the data is collected, it needs to be preprocessed which involves handling missing values, outliers, and applying transformations like feature scaling, normalization, or feature engineering.

3. Exploratory data analysis (EDA): Perform exploratory data analysis to gain insights into the data. This involves visualizing the data, analyzing the distribution, correlation, and relationships between variables. EDA helps in understanding the patterns and trends in the data and guides the feature selection process.

4. Feature selection: Identify the relevant features that are most important for predicting the target variable. This can be done through various techniques like correlation analysis, feature importance using algorithms like Random Forest, or by applying domain knowledge.

5. Model selection: Choose an appropriate machine learning algorithm based on the problem type (e.g., classification, regression) and the nature of the data (e.g., numeric, categorical, text). There are various algorithms to choose from, such as logistic regression, random forest, support vector machines, etc.

6. Model training: Train the chosen model using the prepared dataset. Split the data into training and validation sets, and fit the model to the training data. The model learns from the patterns present in the training data and adjusts its internal parameters accordingly.

7. Model evaluation: Evaluate the performance of the trained model using appropriate evaluation metrics. This could include metrics like accuracy, precision, recall, F1 score, mean squared error, etc. The evaluation helps in determining if the model meets the desired performance criteria.

8. Model tuning: Fine-tune the model by optimizing its hyperparameters to improve its performance. Hyperparameters are parameters that are set before training the model and can be adjusted to enhance model performance, such as learning rate, regularization term, number of layers in a neural network, etc.

9. Model deployment: Once the model is trained and tuned, it can be deployed into a production environment and used for making predictions on new data. This involves creating an interface or API to interact with the model and integrate it into an existing system.

10. Model monitoring and maintenance: Continuous monitoring of the deployed model’s performance is crucial to ensure its effectiveness is maintained over time. As new data becomes available, the model may need to be retrained periodically to adapt to changing patterns or to include new data.

These steps provide a general framework for building machine learning models. However, the specific process may vary depending on the problem at hand and the tools and techniques being used.