Write an advanced usage section

README.md

@@ -144,3 +144,43 @@ Execute the following steps in a PowerShell terminal:
 8. Open [Docker Desktop](https://www.docker.com/products/docker-desktop/) and leave it opened in the background.
 
 Now, open a Git Bash terminal and follow the instructions in the "[Run the script](#run-the-script)" section as well as the subsequent sections. You might need to install Microsoft Visual C++ 14.0 or greater.
+
+## Advanced usage
+
+This chapter is for advanced users who want to further customize the trader agent's behaviour without changing the underlying trading logic.
+
+##### Policy weights
+
+This script automatically sets some default weights to the agent's policy as a warm start 
+to help convergence and improve tool selection. 
+These data were obtained after many days of running the service and are set 
+[here](https://github.com/valory-xyz/trader-quickstart/blob/0f093ebbf0857b8484a017912c3992f00fbe1a29/run_service.sh#L133-L137).
+As a result, the current weights are always deleted and replaced by this strategy 
+which is considered to boost the initial performance of the service.
+
+However, you may have found better performing policy weights and would like to remove this logic. 
+It can easily be done, by removing this method call, 
+[here](https://github.com/valory-xyz/trader-quickstart/blob/0f093ebbf0857b8484a017912c3992f00fbe1a29/run_service.sh#L698), 
+in order to set your own custom warm start. 
+Setting your own custom weights can be done by editing the corresponding files in `.trader_runner`.
+Moreover, you may store your current policy as a backup before editing those files, using the following command:
+
+```shell
+cp ".trader_runner/available_tools_store.json" ".trader_runner/available_tools_store_$(date +"%d-%m-%Y")".json
+```
+
+##### Tool selection
+
+Sometimes, a mech tool might temporarily return invalid results.
+As a result, the service would end up performing mech calls without being able to use the response.
+Assuming that this tool has a large reward rate in the policy weights, 
+the service might end up spending a considerable amount of xDAI before adjusting the tool's reward rate, 
+without making any progress.
+If a tool is temporarily misbehaving, you could use an environment variable in order to exclude it.
+This environment variable is defined 
+[here](https://github.com/valory-xyz/trader/blob/v0.8.0/packages/valory/services/trader/service.yaml#L109-L112) 
+and can be overriden by setting it anywhere in the `run_service.sh` script with a new value, e.g.:
+
+```shell
+IRRELEVANT_TOOLS=["some-misbehaving-tool", "openai-text-davinci-002", "openai-text-davinci-003", "openai-gpt-3.5-turbo", "openai-gpt-4", "stabilityai-stable-diffusion-v1-5", "stabilityai-stable-diffusion-xl-beta-v2-2-2", "stabilityai-stable-diffusion-512-v2-1", "stabilityai-stable-diffusion-768-v2-1"]
+```